U.S. patent application number 09/828930 was filed with the patent office on 2001-08-23 for process and apparatus for filling n2 gas into tire.
Invention is credited to Kobayashi, Yasushi, Makino, Yoshihiro, Sakakibara, Yoshitomo.
Application Number | 20010015237 09/828930 |
Document ID | / |
Family ID | 27519891 |
Filed Date | 2001-08-23 |
United States Patent
Application |
20010015237 |
Kind Code |
A1 |
Makino, Yoshihiro ; et
al. |
August 23, 2001 |
Process and apparatus for filling N2 gas into tire
Abstract
A process for filling N.sub.2 gas into a tire assembled onto a
rim to hold a recommended internal pressure comprises discharging
air inside the tire prior to the filling of N.sub.2 gas to render
the inside of the tire into a state lower than atmospheric pressure
and filling N.sub.2 gas into such a tire. An apparatus for carrying
out the above process comprises a single inlet path, at least two
outlet paths and a membrane module for separating air introduced
through the inlet path into O.sub.2 gas and N.sub.2 gas and feeding
these gases into respective outlet paths, wherein an outlet path
for feeding N.sub.2 gas in the outlet paths is connected at its top
to a valve for inflating a tire assembled onto a rim under an
internal pressure and a discharge path for discharging air inside
the tire prior to the filling of N.sub.2 gas is provided on the way
of such an outlet path.
Inventors: |
Makino, Yoshihiro; (Tokyo,
JP) ; Sakakibara, Yoshitomo; (Tokyo, JP) ;
Kobayashi, Yasushi; (Tokyo, JP) |
Correspondence
Address: |
SUGHRUE, MION, ZINN, MACPEAK & SEAS, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
WASHINGTON
DC
20037-3213
US
|
Family ID: |
27519891 |
Appl. No.: |
09/828930 |
Filed: |
April 10, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09828930 |
Apr 10, 2001 |
|
|
|
09417542 |
Oct 14, 1999 |
|
|
|
6234217 |
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Current U.S.
Class: |
141/1 ; 141/38;
141/95 |
Current CPC
Class: |
B60S 5/046 20130101 |
Class at
Publication: |
141/1 ; 141/38;
141/95 |
International
Class: |
B65B 031/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 14, 1998 |
JP |
10-292,365 |
Oct 14, 1998 |
JP |
10-292,366 |
Oct 14, 1998 |
JP |
10-292,367 |
Jan 26, 1999 |
JP |
11-17,087 |
Jan 27, 1999 |
JP |
11-18,246 |
Claims
What is claimed is:
1. A process for filling N.sub.2 gas into a tire assembled onto a
rim to hold a recommended internal pressure, characterized in that
air inside the tire is discharged prior to the filling of N.sub.2
gas to render the inside of the tire into a state lower than
atmospheric pressure and then N.sub.2 gas is filled into such a
tire.
2. A process for filling N.sub.2 gas into a tire assembled onto a
rim to hold a recommended internal pressure, characterized in that
an operation for discharging out a gas filled in the tire into the
atmosphere is carried out at least one times on the way of filling
N.sub.2 gas.
3. A process for filling N.sub.2 gas into a tire assembled onto a
rim to hold a recommended internal pressure, characterized in that
an operation for discharging out a gas filled in the tire into the
atmosphere is carried out at least one times on the way of filling
N.sub.2 gas.
4. A process for filling N.sub.2 gas into a tire assembled onto a
rim to hold a recommended internal pressure, characterized in that
N.sub.2 gas to be filled into the tire is fed at a pressure
exceeding 1000 kPa and then adjusted to a pressure higher by at
least 100 kPa than the recommended internal pressure to fill into
the tire.
5. A process according to claim 4, wherein N.sub.2 gas is filled in
a pressure not exceeding the feeding pressure of N.sub.2 gas in the
filling into the tire.
6. An apparatus for filling N.sub.2 gas into a tire, comprising a
single inlet path, at least two outlet paths and a membrane module
for separating air introduced through the inlet path into O.sub.2
gas and N.sub.2 gas and feeding these gases into respective outlet
paths, wherein an outlet path for feeding N.sub.2 gas in the outlet
paths is connected at its top to a valve for inflating a tire
assembled onto a rim under an internal pressure and a discharge
path for discharging air inside the tire prior to the filling of
N.sub.2 gas is provided on the way of such an outlet path.
7. An apparatus according to claim 6, wherein at least two membrane
modules are arranged side by side.
8. An apparatus according to claim 6, wherein the air discharge
path is connected to a vacuum pump and a holder storing N.sub.2 gas
fed from the membrane module once is disposed in the outlet path
located at an upstream side from a portion thereof connected to the
air discharge path.
9. An apparatus according to claim 6, wherein a switch valve
properly releasing the internal pressure of the tire is provided on
the outlet path feeding N.sub.2 gas and further a flow control
valve adjusting a flow amount of N.sub.2 gas is arranged on the
outlet path feeding N.sub.2 gas.
10. An apparatus according to claim 6, wherein a pressure adjusting
means for setting pressure to a proper level in accordance with a
recommended internal pressure of the tire is arranged in the outlet
path feeding N.sub.2 gas.
11. An apparatus according to claim 6, wherein the apparatus is
further provided with means for indicating a concentration of
N.sub.2 gas and means for sucking and discharging the remaining air
in the tire by utilizing pressure of compressed air fed into the
membrane module.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to a process and an apparatus for
filling N.sub.2 gas into tires, and more particularly to a process
and an apparatus for efficiently filling N.sub.2 gas inclusive of
N.sub.2 rich gas having a high N.sub.2 concentration into tires
such as passenger car tires, large-size vehicle tires (for truck
and bus) and the like regardless of the kind of the tire used.
[0003] 2. Description of Related Art
[0004] Since N.sub.2 gas is very durable to a temperature change,
when N.sub.2 gas is filled into a tire, even if the temperature of
the tire is raised during the high-speed running, severe service
running or the like, the change of internal pressure in the tire is
small and it is possible to prevent the lowering of the running
performances and it is advantageous to improve the ride comfort.
Therefore, the filling of N.sub.2 gas is adopted in special
applications such as airplanes and F1 racing cars obliged to be run
at a high speed.
[0005] Recently, it is generally and widely known that the filling
of N.sub.2 gas into the tire develops an effect of preventing the
degradation of rubber or wheel and the like. Further, the filling
of N.sub.2 gas tends to be required by ordinary users with the
advance of high tire performances. As a result, the filling of
N.sub.2 gas is particularly carried out as a part of service in car
shops, oil depots and the like. For this end, it is demanded to
develop means for efficiently filling N.sub.2 gas into the tire
with a relatively cheap filling cost.
[0006] As a filling system of N.sub.2 gas, there are known a method
of using a commercially available cylinder filled with N.sub.2 gas
for filling N.sub.2 gas into the tire, a method wherein only
N.sub.2 gas is separated and purified with an industrial activated
carbon while feeding compressed air through an air compressor for
filling N.sub.2 gas, and a method of using a gas separation
membrane wherein O.sub.2 and N.sub.2 are separated from air by
utilizing a theory that permeation rates differ in accordance with
a kind of gas components to thereby feed a high concentration
N.sub.2 gas.
[0007] In the method of using the N.sub.2 filled cylinder, however,
much labor is required in inventory control, carrying-in,
carrying-out and the like of the cylinder and also it is required
to ensure a setting place of the cylinder, so that this method is
disadvantageous in view of the running cost. In the method using
the industrial activated carbon, there is no inconvenience as
mentioned above, but it is necessary that the activated carbon
after the use over a certain time is subjected to a regeneration
treatment for removing O.sub.2 adsorbed on the activated carbon
once and hence the maintenance is inevitable. Particularly, when
the filling of N.sub.2 gas is requested during the regeneration of
the activated carbon, there is an inconvenience that such a request
is not satisfied. And also, the method using the activated carbon
has an advantage of setting the concentration of N.sub.2 gas to an
arbitrary level, but when using the compressed air above 1000 kPa,
a high pressure O.sub.2 gas (active gas) is gathered in a tank of a
high pressure gas installation in view of its structure, so that it
is disadvantageous to regulate a setting place of such an
installation.
[0008] On the other hand, the method using the gas separation
membrane does not cause the drawbacks as mentioned above and can
relatively rapidly fill N.sub.2 gas, if necessary. And also, it is
not required to use a tank gathering a high pressure O.sub.2 gas
even when using a compressed air above 1000 kPa, so that the method
can advantageously be used in wider fields without subjecting to
the regulation for the high pressure gas installation. In this
method, however, it can not be avoid that about 7% of O.sub.2
remains in a passenger car tire even when N.sub.2 gas having a
concentration of 100% is filled into the tire so as to have an
internal pressure of 200 kPa (even if air is merely taken out from
the tire, air equal to atmospheric pressure is existent in the
tire), so that it can not be said to more expect the effect by the
filling of N.sub.2 gas. This is true in the above two methods.
Particularly, a recommended internal pressure is higher in large
size tires for truck and bus than that of the passenger car tire,
so that a long time is unavoidably required in the filling of
N.sub.2 gas into such a large size tire at the present. For this
end, it is strongly demanded to solve these problems.
SUMMARY OF THE INVENTION
[0009] It is, therefore, an object of the invention to provide a
novel process and an apparatus capable of efficiently and rapidly
filling N.sub.2 gas or N.sub.2 rich gas into the tire and visually
grasping concentration of N.sub.2 gas fed to the tire and
concentration of N.sub.2 gas in the tire after the filling.
[0010] According to a first aspect of the invention, there is the
provision of a process for filling N.sub.2 gas into a tire
assembled onto a rim to hold a recommended internal pressure,
characterized in that air inside the tire is discharged prior to
the filling of N.sub.2 gas to render the inside of the tire into a
state lower than atmospheric pressure and then N.sub.2 gas is
filled into such a tire. In this case, N.sub.2 gas includes N.sub.2
rich gas having a high N.sub.2 concentration.
[0011] According to a second aspect of the invention, there is the
provision of a process for filling N.sub.2 gas into a tire
assembled onto a rim to hold a recommended internal pressure,
characterized in that an operation for discharging out a gas filled
in the tire into the atmosphere is carried out at least one times
on the way of filling N.sub.2 gas.
[0012] According to a third aspect of the invention, there is the
provision of a process for filling N.sub.2 gas into a tire
assembled onto a rim to hold a recommended internal pressure,
characterized in that an operation for discharging out a gas filled
in the tire into the atmosphere is carried out at least one times
on the way of filling N.sub.2 gas. In this case, an adjustment of
controlling a flow amount of N.sub.2 gas is carried out in the
filling of N.sub.2 Gas.
[0013] According to a fourth aspect of the invention, there is the
provision of a process for filling N.sub.2 gas into a tire
assembled onto a rim to hold a recommended internal pressure,
characterized in that when large size tires for use in trucks,
busses and the like are used as the tire, N.sub.2 gas to be filled
into the tire is fed at a pressure exceeding 1000 kPa and then
adjusted to a pressure higher by at least 100 kPa than the
recommended internal pressure to fill into the tire.
[0014] In a preferable embodiment of the fourth aspect, N.sub.2 gas
is filled in a pressure not exceeding the feeding pressure of
N.sub.2 gas in the filling into the tire.
[0015] In the filling of N.sub.2 gas into the large size tire, air
inside the tire may be discharged prior to the filling of N.sub.2
gas to render the inside of the tire into a state lower than
atmospheric pressure, or an operation for discharging out a gas
filled in the tire into the atmosphere may be carried out at least
one times on the way of filling N.sub.2 gas.
[0016] In any case, N.sub.2 gas is filled by adjusting the feeding
pressure of N.sub.2 gas so as to fit into the recommended internal
pressure of the tire assembled onto the rim.
[0017] According to a fifth aspect of the invention, there is the
provision of an apparatus for filling N.sub.2 gas into a tire,
comprising a single inlet path, at least two outlet paths and a
membrane module for separating air introduced through the inlet
path into O.sub.2 gas and N.sub.2 gas and feeding these gases into
respective outlet paths, wherein an outlet path for feeding N.sub.2
gas in the outlet paths is connected at its top to a valve for
inflating a tire assembled onto a rim under an internal pressure
and a discharge path for discharging air inside the tire prior to
the filling of N.sub.2 gas is provided on the way of such an outlet
path.
[0018] In a preferable embodiment of the apparatus according to the
invention, at least two membrane modules are arranged side by side.
In another preferable embodiment of the apparatus, the air
discharge path is connected to a vacuum pump and a holder storing
N.sub.2 gas fed from the membrane module once is disposed in the
outlet path located at an upstream side from a portion thereof
connected to the air discharge path.
[0019] In the other preferable embodiment of the apparatus, a
switch valve properly releasing the internal pressure of the tire
is provided on the outlet path feeding N.sub.2 gas and further a
flow control valve adjusting a flow amount of N.sub.2 gas is
arranged on the outlet path feeding N.sub.2 gas.
[0020] In the apparatus according to the invention, a pressure
adjusting means for setting pressure to a proper level in
accordance with a recommended internal pressure of the tire may be
arranged in the outlet path feeding N.sub.2 gas. And also, means
for indicating a concentration of N.sub.2 gas may be arranged, and
further means for sucking and discharging the remaining air in the
tire by utilizing pressure of compressed air fed into the membrane
module may be arranged. A pressure reducing valve may be used as
the pressure adjusting means.
[0021] The outlet path feeding N.sub.2 gas through the membrane
module is divided into two branched pathways, one of which pathways
being used as a pathway feeding N.sub.2 gas at a higher pressure
adaptable for a large-size tire used in vehicles such as truck, bus
and the like and the other pathway being used as a pathway feeding
N.sub.2 gas at a relatively low pressure adaptable for a passenger
car tire or the like. In this case, the term "relatively low
pressure" used herein means a pressure of about 200-550 kPa, and
the term "higher pressure" means a pressure of about 550-1400
kPa.
[0022] According to the invention, when the recommended internal
pressure is held in the tire assembled onto the rim by filling
N.sub.2 gas, it is favorable that the concentration of N.sub.2 gas
fed into the tire is continuously measured by means of a sensor
during the filling of N.sub.2 gas to indicate the measured result
through an indicating means at any time, or the concentration of
N.sub.2 gas in the tire after the completion of the filling of
N.sub.2 gas is measured to indicate the measured result through an
indicating means. For this end, the apparatus according to the
invention is provided with an indicating means for indicating at
least one of the N.sub.2 gas concentration fed into the tire during
the filling of N.sub.2 gas and the N.sub.2 gas concentration in the
tire after the completion of the filling of N.sub.2 gas. In this
case, an indicator indicating the measured value through the sensor
for the measurement of N.sub.2 gas concentration is used as the
indicating means. In the invention, the indicator is favorable to
be a digital indicator.
[0023] In the outlet path feeding N.sub.2 gas may be arranged a
discharge path for discharging a gas inside the tire. And also, a
four-port valve used for measuring the N.sub.2 gas concentration in
the tire after the filling of N.sub.2 gas may be arranged between a
portion of the outlet path connected to the discharge path and the
membrane module. Particularly, a valve of closed center system is
favorably used as the four-port valve.
[0024] When the N.sub.2 gas separated from the compressed air is
filled into the tire assembled onto the rim, air remaining in the
tire may be sucked and discharged by utilizing the pressure of the
compressed air prior to the filling of N.sub.2 gas to render the
inside of the tire into a state lower than atmospheric pressure. In
this case, the discharge of the remaining air is favorable to be
carried out by using an ejector.
[0025] When a remaining air discharge means for sucking and
discharging the remaining air from the inside of the tire by
utilizing the pressure of the compressed air fed into the membrane
module is arranged in the apparatus according to the invention, the
membrane module is constructed with at least one inlet path
introducing the compressed air and at least two outlet paths
flowing N.sub.2 gas and O.sub.2 gas, and the remaining air
discharge means is arranged between the inlet path introducing the
compressed air and the outlet flowing N.sub.2 gas.
[0026] In this case, it is desirable that an ejector utilizing the
pressure of the compressed air introduced into the membrane module
is used as the remaining air discharge means, and a sensor
measuring the N.sub.2 gas concentration and an indicating means for
indicating the measured value through the sensor are arranged in
the outlet path feeding N.sub.2 gas so as to visually confirm the
N.sub.2 gas concentration.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] The invention will be described with reference to the
accompanying drawings, wherein:
[0028] FIG. 1 is a schematic view illustrating a first embodiment
of the apparatus for filling N.sub.2 gas according to the
invention;
[0029] FIG. 2 is a diagrammatic view of T-type cock suitably used
in the invention;
[0030] FIG. 3 is a schematic view illustrating a second embodiment
of the apparatus for filling N.sub.2 gas according to the
invention;
[0031] FIG. 4 is a perspective view of the apparatus shown in FIG.
3;
[0032] FIG. 5 is a schematic view illustrating a third embodiment
of the apparatus for filling N.sub.2 gas according to the
invention;
[0033] FIG. 6 is a schematic view illustrating a fourth embodiment
of the apparatus for filling N.sub.2 gas according to the
invention;
[0034] FIG. 7 is a schematic view illustrating a fifth embodiment
of the apparatus for filling N.sub.2 gas according to the
invention;
[0035] FIG. 8 is a diagrammatically section view of an ejector;
and
[0036] FIG. 9 is a graph showing a relation between a concentration
of N.sub.2 gas and a filling pressure thereof.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0037] In the invention, when N.sub.2 gas inclusive of N.sub.2 rich
gas is filled into the tire, once air inside the tire is discharged
prior to the filling of N.sub.2 gas to render the inside of the
tire into a state lower than atmospheric pressure, N.sub.2 gas is
filled into such a tire, so that air remaining in the tire,
particularly O.sub.2 gas becomes very small and hence it can be
expected to more develop the effect by the filling of N.sub.2
gas.
[0038] When the inside of the tire is rendered into a state lower
than atmospheric pressure by discharging air from the tire prior to
the filling of N.sub.2 gas, or when N.sub.2 gas is filled without
discharging air from the inside of the tire up to a pressure lower
than atmospheric pressure, an operation for discharging out a gas
filled in the tire into the atmosphere is carried out at least one
times on the way of filling N.sub.2 gas, whereby it is possible to
replace O.sub.2 gas remaining in the tire with N.sub.2 gas to
increase the concentration of N.sub.2 gas in the tire. In this
case, the amount Of O.sub.2 gas remaining in the tire can be made
very small by repeating the above operation several times.
[0039] When N.sub.2 gas is fed at a pressure exceeding 1000 kPa and
then the pressure is adjusted to a level higher by at least 100 kPa
than the recommended internal pressure in the filling of N.sub.2
gas into the tire, N.sub.2 gas can efficiently be filled up to the
recommended internal pressure in tires for airplanes and the
like.
[0040] Since the recommended internal pressure in the large-size
tires for truck, bus and the like is usually about 600-900 kPa,
when N.sub.2 gas is filled into the large-size tire in the
invention, N.sub.2 gas is first fed at a pressure exceeding 1000
kPa (even if the pressure exceeds 1000 kPa in a first class gas
such as N.sub.2 gas defined in enforcement regulations of high
pressure gas preservation law, the regulation is not applied when
the pressure is not more than 5000 kPa) and then filled into the
tire by adjusting the filling pressure of N.sub.2 gas to a pressure
higher by at least 100 kPa than the recommended internal pressure
for the tire without exceeding the feeding pressure of the N.sub.2
gas, whereby N.sub.2 gas can be filled up to the recommended
internal pressure for a relatively short time.
[0041] In the passenger car tires or the large-size tires for truck
and bus, when the feeding pressure of N.sub.2 gas is adjusted so as
to match with the internal pressure for the tire assembled onto the
rim, N.sub.2 gas can efficiently be filled into the tire
irrespectively of the kind of the tires.
[0042] When the N.sub.2 gas concentration in the tire during the
filling or the N.sub.2 gas concentration in the tire after the
filling is measured by a sensor for the N.sub.2 gas concentration
and the measured value is indicated in the indicating means, the
state of filling N.sub.2 gas can be grasped by not only the
operator but also the user, which contributes to enhance the
reliability.
[0043] As the sensor may be used, for example, an O.sub.2 sensor.
In this case, the concentration of O.sub.2 gas included in N.sub.2
gas during the feeding or retained in the tire is measured, from
which the N.sub.2 gas concentration can be calculated as
(100-O.sub.2 gas concentration) %. And also, use may be made of a
sensor capable of directly measuring the N.sub.2 gas
concentration.
[0044] When air remaining in the inside of the tire is sucked by
utilizing the pressure of the compressed air introduced for the
formation of N.sub.2 gas, a certain line for the utilization of the
pressure of the compressed air may be added to the apparatus and
also an operation therefor is basically carried out only by
adjusting the pressure of the compressed air.
[0045] In FIG. 1 is shown a first embodiment of the apparatus for
filling N.sub.2 gas according to the invention provided with two
membrane modules made of a hollow fiber membrane or the like and
arranged side by side. In FIG. 1, numeral 1 is an inlet path for
feeding a compressed air from a compressor (not shown) into
membrane modules m.sub.1, m.sub.2, wherein the inlet path 1 is
divided into two pathways 1a, 1b in the vicinity of the membrane
modules m.sub.1, m.sub.2. And also, numeral 2 is a switch valve,
numeral 3 a regulator provided with a pressure gauge (pressure
reducing valve), numeral 4 an air filter removing contaminant from
air, and numeral 5 a mist filter. The switch valve 2, regulator 3,
air filter 4 and mist filter 5 are arranged in the inlet path 1 in
this order.
[0046] Further, numeral 6 is a switch valve arranged in the pathway
1a for the membrane module m.sub.1 branched from the inlet path 1,
and numeral 7 a switch valve arranged in the pathway 1b for the
membrane module m.sub.2 branched from the inlet path 1. These
switch valves 6, 7 serve to feed the compressed air into the
membrane modules m.sub.1, m.sub.2 and stop the feeding thereof
through the on-off operation. Numerals 8, 9 are outlet paths from
the membrane modules m.sub.1, m.sub.2, wherein the outlet path 8 is
a path feeding N.sub.2 gas and the outlet path 9 is a path
discharging O.sub.2 gas (including O.sub.2 rich gas).
[0047] And also, numerals 10a, 10b are switch valves arranged in
the outlet path 8 for the membrane modules m.sub.1, m.sub.2,
numeral 11 a pressure gauge measuring the pressure inside the
outlet path 8, and numeral 12 an oxygen concentration measuring
meter for measuring the concentration of O.sub.2 gas in the outlet
path 8. The meter 12 is connected to the outlet path 8 through a
pressure reducing valve 13 provided with a pressure gauge and a
flow control valve 14.
[0048] Numeral 15 is a holder capable of storing N.sub.2 gas fed
from the membrane modules m.sub.1, m.sub.2, if necessary, and
numeral 16 a switch valve having a function capable of adjusting a
flow amount of N.sub.2 gas in the outlet path 8. Numeral 17 is a
discharge path connecting to the outlet path 8 at a downstream side
of the switch valve 16. In the discharge path 17 is arranged a
switch valve 18 connecting to a vacuum pump P, whereby air inside
the tire assembled onto the rim can be discharged through the
discharge path 17 to render the inside of the tire into a state
lower than atmospheric pressure. Further, numeral 19 is a switch
valve capable of discharging gas filled in the tire, if
necessary.
[0049] Prior to the filling of internal pressure into the tire
assembled onto the rim, air is existent in the inside of the tire
and is comprised of about 80% N.sub.2 and about 20% O.sub.2. In
case of the passenger car tire, the internal pressure is about 200
kPa, so that even when N.sub.2 gas having a concentration of 100%
is filled into the tire, the concentration of N.sub.2 gas in the
tire is about 93% and about 7% of O.sub.2 gas is included in the
tire. Therefore, in order to more develop the effect by the filling
of N.sub.2 gas, it is required to further reduce O.sub.2 gas in the
tire.
[0050] The filling of N.sub.2 gas into the tire assembled onto the
rim is carried out by using the apparatus of the above construction
as follows.
[0051] 1. In case of filling of N.sub.2 gas once air inside the
tire is discharged
[0052] At first, a top of the outlet path 8 is connected to a gas
filling valve of the tire assembled onto the rim and then the
switch valves 16 and 19 in the outlet path 8 are closed, while the
switch valve 18 in the discharge path 17 is opened to discharge air
in the tire under the working of the pump P. Then, the switch valve
18 is closed and at the same time the switch valve 16 is opened to
fill N.sub.2 gas fed from the membrane modules m.sub.1, m.sub.2
into the tire through the outlet path 8.
[0053] 2. In case of filling N.sub.2 gas without discharging air
remaining in the tire and conducting an operation of discharging
the filled gas toward atmosphere on the way of the filling at least
one times
[0054] At first, a top of the outlet path 8 for N.sub.2 gas is
connected to a valve of the tire and the switch valve 16 is opened,
while the switch valves 18 and 19 are closed to fill N.sub.2 gas
into the tire. At a time of reaching the internal pressure of the
tire to a given pressure, or at a time of attaining a give filling
time, the switch valve 16 is closed to stop the filling of N.sub.2
gas, while the switch valve 19 is opened to discharge the filled
gas in the tire and then the switch valve 19 is closed and the
switch valve 16 is again opened to fill N.sub.2 gas into the tire
so as to reach up to the recommended internal pressure. The filling
of N.sub.2 gas and the discharge of the filled gas are repeated one
time or more, if necessary.
[0055] During the discharge of the filled gas in the tire, the
valve of the tire is always connected to the top of the outlet path
8.
[0056] In the invention, the discharge of the filled gas and the
filling of N.sub.2 gas can be carried out by working the switch
valve 15a and the switch valve 19, but such an operation may be
conducted by using a T-shaped cock t as shown in FIG. 2.
[0057] The filling of N.sub.2 gas is carried out as follows.
[0058] At first, the switch valves 2, 6, 7, 10a, 10b, 15a are
opened, while the switch valves 15b, 15c, 16 and the regulator 3
are closed. Then, compressed air is introduced from the compressor
into the inlet path 1 and the pressure of the compressed air is
gradually raised to a given value by adjusting the regulator 3.
[0059] As the membrane module arranged in the apparatus is used,
for example, a separation membrane made of polyimide. By utilizing
a difference of permeation rate produced when the compressed air is
passed through such a membrane, O.sub.2 gas is removed, while a
high concentration N.sub.2 gas is obtained. The feeding pressure of
N.sub.2 gas is set to a given value by considering that the
pressure in the outlet path for the membrane modules m.sub.1,
m.sub.2 indicates a value lower by about 50-100 kPa than the
pressure in the regulator 3.
[0060] The accurate measurement of the concentration in the oxygen
concentration meter 12 arranged in the outlet path 8 is carried out
by the pressure adjustment through the pressure reducing valve 13
and the flowing amount adjustment through the flow control valve
14, whereby the feeding of high concentration N.sub.2 gas is
confirmed to fill N.sub.2 gas into the tire assembled onto the
rim.
[0061] When the feeding pressure of N.sub.2 gas is too low in the
working of the apparatus, the switch valves 6 and 10a or the switch
valves 7 and 10b are closed to use either one of the membrane
modules because, when only the switch valve 6 or 7 is closed, the
gas flows backward into the module so as not to raise the
pressure.
[0062] According to the invention, when a half of air in the tire
is discharged prior to the filling of N.sub.2 gas and then N.sub.2
gas is filled by using the above apparatus, the O.sub.2
concentration after the filling up to the internal pressure is
about 5%. Alternatively, after N.sub.2 gas is filled into the tire
assembled onto the rim so as to obtain an internal pressure of 200
kPa without discharging air in the tire, the filled gas is
discharged toward atmosphere until the internal pressure of the
tire is 100 kPa, and then N.sub.2 gas is again filled up to a given
internal pressure, whereby the O.sub.2 concentration can be reduced
to about 5% after the filling to the internal pressure.
[0063] When N.sub.2 gas is filled into the tire assembled onto the
rim so as to render the internal pressure into 400 kPa without
discharging air in the tire and thereafter the filled gas is
discharged toward atmosphere until the internal pressure of the
tire is 0 kPa and then N.sub.2 gas is again filled up to the
internal pressure, the O.sub.2 concentration is reduced to about 3%
after the filling to the internal pressure.
[0064] When air in the tire is discharged prior to the filling of
N.sub.2 gas, it is required to conduct deaeration by using the
vacuum pump, wherein O.sub.2 can be rendered into substantially a
free state in accordance with the discharging degree of air from
the inside of the tire. On the other hand, the operation that
N.sub.2 gas is filled up to the internal pressure and the filled
gad is discharged into atmosphere and then N.sub.2 gas is again
filled up to the internal pressure is repeated several times,
whereby it is possible to considerably reduce the concentration of
O.sub.2 remaining in the tire. Thus, the filling degree of N.sub.2
gas can be increased even in these cases.
[0065] In the N.sub.2 gas filling apparatus provided with the
membrane modules, when the flow amount of N.sub.2 gas per unit time
is decreased by using, for example, the flow control function of
the switch valve 16 as compared with the flow amount of the
compressed air per unit time in the inlet path 1, the pressure in
the membrane module rises with the decrease of the flow amount of
N.sub.2 gas (pressure in the membrane module is not less than 1000
kPa, preferably not less than 1050 kPa) and hence the concentration
of N.sub.2 gas rises (though the separation into O.sub.2 gas and
N.sub.2 gas takes a long time) to obtain N.sub.2 gas more suitable
for filling into the tire. In this case, however, it tends to
prolong the time filling such N.sub.2 gas into the tire. For this
end, it is favorable that in order to fill N.sub.2 gas having a
higher concentration, such N.sub.2 gas previously stored in a
holder 15 may be supplied from the holder 15 to the tire in
accordance with the user's request.
[0066] When N.sub.2 gas is charged into the holder 15, switch
valves 15a and 15c are closed, while a switch valve 15b is
opened.
[0067] A gas discharged through the outlet path 9 is O.sub.2 rich
gas having O.sub.2 concentration of about 35%, so that it is
particularly required to select a place separated away from fire,
combustibles and the like and being well ventilated.
[0068] Although an embodiment of arranging two membrane modules
m.sub.1, m.sub.2 side by side is shown in FIG. 1, these modules may
be arranged in series or a single membrane module may be used.
Particularly, the number of the membrane modules is not
restricted.
[0069] Even in the large-size tires, N.sub.2 gas can be filled in
the same manner as mentioned above. In this case, the pressure of
the compressed air in the inlet path 1 is set to about 1100 kPa,
and the pressure of N.sub.2 gas in the outlet path 8 is set to
about 970 kPa.
[0070] In FIG. 3 is shown a second embodiment of the N.sub.2 gas
filling apparatus according to the invention provided with a single
membrane module, and an exterior appearance of the apparatus of
FIG. 3 is shown in FIG. 4.
[0071] In the apparatus shown in FIG. 3, the outlet path 8 is
divided at its downstream side into a pathways 8a feeding N.sub.2
gas of a high pressure suitable for filling into tires for truck,
bus and the like (TB) and a pathway 8b feeding N.sub.2 gas of a low
pressure suitable for filling into a tire for passenger car and the
like (PS), wherein top portions of these pathways may be connected
to gas filling valves (not shown) for the respective tires,
respectively. In FIG. 3, numeral 20 is a pressure gauge arranged in
the pathways 8a, numeral 21 a regulator arranged in the pathway 8b,
and numeral 22 a pressure gauge arranged in the pathway 8b.
[0072] When N.sub.2 gas is filled into a passenger car tire
assembled onto a rim by using the apparatus of FIG. 3, the filling
of N.sub.2 gas is carried out by adjusting a pressure of N.sub.2
gas fed from the membrane module m to a value corresponding to a
recommended internal pressure of the tire through the regulator 21
arranged in the pathway 8b. In this case, the valve arranged at the
top of the pathway 8a is closed.
[0073] When a high pressure N.sub.2 gas is filled into a large-size
tire assembled onto a rim, the filling of N.sub.2 gas is carried
out by feeding N.sub.2 gas from the membrane module m through the
pathway 8a and the valve arranged at its top into the tire. In this
case, the valve arranged at the top of the pathway 8b is
closed.
[0074] Although the outlet path 8 of the module m is divided into
the pathway 8a for high pressure N.sub.2 gas and the pathway 8b for
low pressure N.sub.2 gas shown in FIG. 3, the filling of N.sub.2
gas may be carried out by arranging a pressure adjusting means in
the outlet path without division and adjusting the filling pressure
to a value corresponding to a recommended internal pressure of the
respective tire.
[0075] In the apparatus of FIG. 3, a holder may be arranged in the
outlet path 8 likewise the case of FIG. 1 and N.sub.2 gas may be
stored therein. Thus, it is possible to quickly cope with various
kinds of the tires.
[0076] When N.sub.2 gas is filled into the tire at a higher
concentration by decreasing air remaining in the tire, as shown in
FIG. 5, discharge paths 23, 24 are separately arranged in the
pathways 8a, 8b of the outlet path 8 shown in FIG. 3, whereby air
remaining in the tire is discharged through vacuum pump (not shown)
prior to the filling of N.sub.2 gas to render the inside of the
tire into a state lower than atmospheric pressure and then N.sub.2
gas is filled into the tire. When N.sub.2 gas is filled after air
remaining in the tire is discharged once, the switch valve 10 in
the outlet path is closed and air remaining in the tire is
discharged through the discharge path 23, 24 and the vacuum pump as
shown in FIG. 5 and thereafter the switch valve 10 is opened to
conduct the filling of N.sub.2 gas.
[0077] In order to more decrease air remaining in the tire without
conducting the operation of discharging air as mentioned above, it
is favorable to discharge the gas filled in the tire into
atmosphere at least one times on the way of the filling of N.sub.2
gas. In this case, air remaining in the tire can be replaced with
N.sub.2 gas, so that the concentration of N.sub.2 gas in the tire
can be increased. Concretely, the top of the outlet path 8 is
connected to the valve for the tire to feed N.sub.2 gas to the
tire. At a time of arriving the internal pressure of the tire to a
given value or taking a given feeding time, the feed of N.sub.2 gas
is stopped and the gas filled into the tire is discharged and then
N.sub.2 gas is again filled into the tire so as to obtain a
pressure level corresponding to the recommended internal pressure
of the tire.
[0078] In case of using the apparatus shown in FIGS. 3 and 5, the
feeding of N.sub.2 gas is carried out as follows.
[0079] The switch valve 2 is opened, while the regulator 3 is
closed. Then, compressed air is introduced into the inlet path 1
through the compressor, during which the regulator 3 is adjusted to
gradually raise the feeding pressure to a given level.
[0080] In this case, the pressure in the outlet path 8 for the
membrane module m indicates a value lower by about 50-100 kPa than
the pressure in the regulator 3. Considering this fact, the feeding
pressure of N.sub.2 gas is set likewise the apparatus of FIG.
1.
[0081] Moreover, an oxygen concentration meter (not shown) is
arranged in the outlet path 8 to confirm the concentration of
N.sub.2 gas passing through the outlet path 8 during the filling of
N.sub.2 gas into the tire assembled onto the rim.
[0082] Even in the apparatus shown in FIG. 3 or 5, the O.sub.2
concentration after the filling up to the internal pressure can be
rendered into about 5% by discharging a half of air from the inside
of the tire prior to the filling of N.sub.2 gas and then filling
N.sub.2 gas into the tire. Alternatively, after N.sub.2 gas is
filled into the tire assembled onto the rim so as to obtain an
internal pressure of 200 kPa without discharging air in the tire,
the filled gas is discharged toward atmosphere until the internal
pressure of the tire is 100 kPa, and then N.sub.2 gas is again
filled up to a given internal pressure, whereby the O.sub.2
concentration can be reduced to about 5% after the filling to the
internal pressure.
[0083] In the N.sub.2 gas filling apparatus provided with the
membrane module as shown in FIGS. 3 and 5, when the flow amount of
N.sub.2 gas per unit time is decreased by arranging, for example, a
flow control valve in the outlet path 8 as compared with the flow
amount of the compressed air per unit time in the inlet path 1, the
pressure in the membrane module rises with the decrease of the flow
amount of N.sub.2 gas (in case of the large-size tire for truck and
bus, the feeding pressure is set to about 1000 kPa) and hence the
concentration of N.sub.2 gas rises (though the separation into
O.sub.2 gas and N.sub.2 gas takes a long time) to obtain N.sub.2
gas more suitable for filling into the tire. In case of conducting
an operation that the gas filled in the tire is discharged once on
the way of filling the gas, it tends to prolong the time filling
N.sub.2 gas into the tire at a higher concentration up to a
pressure corresponding to the recommended internal pressure of the
tire. For this end, it is favorable that a holder may be arranged
in the outlet path 8 even in the apparatus as shown in FIG. 3 or 5
so as to fill N.sub.2 gas having a higher concentration for a short
time.
[0084] In FIG. 6 is shown a fourth embodiment of the apparatus for
filling N.sub.2 gas according to the invention provided with an
indicating means for indicating the concentration of N.sub.2 gas,
wherein numeral 25 is an air dryer arranged in the inlet path 1,
numeral 26 a pressure reducing valve arranged in the outlet path 8
for adjusting the pressure of N.sub.2 gas, numeral 27 a pressure
gauge, numeral 28 a closed center valve (4 port valve), numeral 29
a compound pressure gauge, and numeral 30 a hand valve for
conducting the feeding and stop of N.sub.2 gas.
[0085] And also, numeral 31 is a discharge path connected to the
outlet path 8 and provided at its top with a vacuum pump (not
shown) for discharging air remaining in the tire through the outlet
path 8, numeral 32 a measuring path connected to the outlet path 8
likewise the discharge path 31 and used for measuring concentration
of N.sub.2 gas passing through the outlet path or N.sub.2 gas in
the tire after the filling into the tire. In the measuring path 32
are arranged a flow control valve 33, an O.sub.2 sensor module 34,
an amplifier 35 for amplifying a signal measured in the O.sub.2
sensor module 32, and an indicator 36 indicating the amplified
signal as a numerical value.
[0086] When N.sub.2 gas is filled into the tire assembled onto the
rim up to the recommended internal pressure of the tire, the switch
valve 2 arranged in the inlet path 1 is opened, while the hand
valve 30 arranged in the outlet path 8 is closed and compressed air
is introduced into the inlet path 1 through a compressor (not
shown).
[0087] The compressed air introduced into the inlet path 1 is fed
into the membrane module m through an air filter 4, an air dryer 25
and a mist filter 5. Then, O.sub.2 gas separated in the membrane
module m (oxygen rich gas) is discharged out through an outlet path
9. On the other hand, N.sub.2 gas (N.sub.2 rich gas) is set to a
pressure higher by about 50-100 kPa than a recommended internal
pressure of a tire by a pressure reducing valve 26 arranged at a
downstream side of the membrane module m and passed through the
outlet path 8 to fill into the tire. In this case, the discharge
path 31 is closed through a switch valve (not shown).
[0088] During the N.sub.2 gas filling, N.sub.2 gas is also flowed
into the measuring path 32 to measure the concentration of O.sub.2
gas included in N.sub.2 gas by the O.sub.2 sensor module 34, and
the measured value is converted into the concentration of N.sub.2
gas according to N.sub.2=(100-O.sub.2) % in such sensor module and
digitally indicated in the indicator 36 through the amplifier 35.
Since N.sub.2 gas is always flowed into the measuring path 32 until
the filling of N.sub.2 gas is completed, the flow control valve 33
is adjusted so as to flow N.sub.2 gas in a slight amount and the
measured gas is discharged out through an outlet port formed in the
sensor module 34 into atmosphere.
[0089] When the concentration of N.sub.2 gas is measured in the
apparatus shown in FIG. 6, the pressure inside the tire is somewhat
decreased, but there is caused no problem when N.sub.2 gas is
previously filled to a pressure slightly higher than the
recommended internal pressure of the tire.
[0090] Although the measurement of N.sub.2 gas concentration is
described by separately arranging the measuring path in the outlet
path of the apparatus shown in FIG. 6, the sensor module 34 and the
like for measuring the N.sub.2 gas concentration may directly be
arranged in the outlet path 8.
[0091] In the N.sub.2 gas filling apparatus as mentioned above, it
is possible to accurately grasp the change of N.sub.2 gas
concentration in the tire during the filling of N.sub.2 gas and
confirm the N.sub.2 gas concentration inside the tire after the
completion of the filling, so that a higher reliability can be
given to a user requesting the filling of N.sub.2 gas.
[0092] As the O.sub.2 sensor module, use may be made of Fujikura
oxygen sensor of linear voltage output type (FCX-MVL) and the like,
while Omron type K3NX digital panel meter and the like may be used
as the indicator.
[0093] In order to more develop the effect by the filling of
N.sub.2 gas by removing air remaining in the tire, even in the
apparatus shown in FIG. 6, there can be carried out an operation
that air inside the tire is discharged prior to the filling of
N.sub.2 gas to render the inside of the tire into a state lower
than atmospheric pressure. If the inside of the tire can not be
rendered into a state lower than atmospheric pressure by removing
air in the tire, an operation that the gas filled in the tire is
discharged into atmosphere on the way of filling N.sub.2 gas and
thereafter N.sub.2 gas is again filled is carried out at least one
times to replace O.sub.2 remaining in the tire with N.sub.2 gas,
whereby it is possible to increase the N.sub.2 gas concentration
inside the tire. By repeating the discharge of the filled gas and
the filling of N.sub.2 gas plural times can be further decreased
the amount of O.sub.2 gas remaining in the tire likewise the cases
of FIGS. 1, 3 and 5.
[0094] When air inside the tire is discharged once and N.sub.2 gas
is again filled in the apparatus shown in FIG. 6, the pressure
reducing valve 26 is closed on the way of the N.sub.2 gas filling
and air remaining in the tire is removed out through the discharge
path 31, and thereafter the discharge path 31 is closed and the
filling of N.sub.2 gas is again carried out in the same manner as
previously mentioned. On the other hand, when N.sub.2 gas is filled
without discharging air remaining in the tire and the discharge of
gas filled in the tire is discharged into atmosphere at least one
times on the way of the N.sub.2 gas filling, after the filling of
N.sub.2 gas is first carried out, the feeding of N.sub.2 gas is
stopped at a time of arriving the pressure inside the tire to a
given value or at a time of taking a given filling time and the
discharge path is opened to discharge the filled gas (into
atmosphere, if necessary) and then the discharge path 31 is closed
and N.sub.2 gas is again filled up to a pressure corresponding to
the recommended internal pressure of the tire. The filling of
N.sub.2 gas and the discharge of the filled gas may be repeated two
or more times, if necessary.
[0095] When N.sub.2 gas is filled after a half of air inside the
tire is discharged in the apparatus shown in FIG. 6, the O.sub.2
concentration is about 3% after the filling into the recommended
internal pressure. On the other hand, after N.sub.2 gas is filled
into the tire assembled onto the rim so as to obtain an internal
pressure of 200 kPa without discharging air in the tire, the filled
gas is discharged toward atmosphere until the internal pressure of
the tire is 100 kPa, and then N.sub.2 gas is again filled up to a
given internal pressure, whereby the O.sub.2 concentration can be
reduced to about 5% after the filling to the internal pressure.
[0096] Even in the N.sub.2 gas filling apparatus provided with the
membrane module as shown in FIG. 6, when the flow amount of N.sub.2
gas per unit time is decreased as compared with the flow amount of
the compressed air per unit time in the inlet path 1, the pressure
in the membrane module rises with the decrease of the flow amount
of N.sub.2 gas and hence the concentration of N.sub.2 gas rises to
obtain N.sub.2 gas more suitable for filling into the tire likewise
the cases of FIGS. 1 and 3. However, it tends to prolong the time
filling N.sub.2 gas into the tire up to a pressure corresponding to
the recommended internal pressure of the tire. For this end, it is
favorable that a holder previously storing N.sub.2 gas is be
arranged in the outlet path 8 for avoiding the prolonging of the
filling time.
[0097] In the apparatus of FIG. 6, the relation between the
pressure in the filling of N.sub.2 gas and the N.sub.2 gas
concentration can be grasped with the lapse of time, so that it is
possible to control the capacity of the membrane module m (capacity
for separation of the gas) by always checking the relation between
pressure and concentration in the filling of N.sub.2 gas.
[0098] In FIG. 7 is shown a fifth embodiment of the apparatus for
filling N.sub.2 gas according to the invention, wherein an air
discharging means for sucking and discharging air remaining in the
tire is provided on the apparatus shown in FIG. 6.
[0099] In FIG. 7, numeral 37 is a flow channel connected to the
inlet path 1 for flowing the compressed air passed through the
inlet path 1, numeral 38 a pressure reducing valve arranged in the
channel 37, numeral 39 a hand valve arranged between the channel 37
and the discharge path 31, and numeral 40 an ejector discharging
out air included in the tire by utilizing the pressure of the
compressed air.
[0100] In order to hold the inside of the tire assembled onto the
rim at the recommended internal pressure by filling N.sub.2 gas,
the switch valve 2 arranged in the inlet path 1 is first opened,
while the closed center valve 28 arranged in the outlet path 8 is
closed and the compressed air is introduced into the inlet path 1
through a compressor (not shown).
[0101] The compressed air is fed into the membrane module m to
separate into O.sub.2 gas and N.sub.2 gas, while a part of the
compressed air is passed through the channel 37 and discharged out
from an outlet port of the ejector 40 through the pressure reducing
valve 38 and hand valve 39 into atmosphere.
[0102] At this state, the hand valves 30 and 39 are opened to
reduce the pressure in the outlet path 8 and the discharge path 31,
whereby air remaining in the tire connected to the top of the
outlet path 8 is sucked and discharged out from the ejector 40
through the outlet path 8 and the discharge path 31.
[0103] The degree of reducing the pressure differs in accordance
with the kind of the tire to be filled with N.sub.2 gas, so that
the value of the reduced pressure is confirmed by the compound
pressure gauge 29. If the pressure is reduced to an extent causing
no rim chafing, a port of the hand valve 39 connecting to the
discharge path 31 is closed. Then, the closed center valve 28 is
opened to fill N.sub.2 gas into the tire (N.sub.2 gas is set to a
pressure higher by about 50-100 kPa than the recommended internal
pressure of the tire by the pressure reducing valve 26 arranged at
the downstream side of the membrane module m).
[0104] Even in the illustrated embodiment, aromatic polyimide
hollow fiber membrane is used, for example, as a separation
membrane of the membrane module m and is set so as to withstand to
a pressure of about 1400 kPa.
[0105] The flow control valve 33 is closed at the time of pressure
reduction or discharging out the remaining air from the tire and
opened so as to pass N2 gas in the filling of N.sub.2 gas, whereby
the O.sub.2 concentration in N.sub.2 gas is measured and converted
into N.sub.2 gas concentration according to N.sub.2=(100- O.sub.2)
% by the O.sub.2 sensor module 34 and amplified in the amplifier 35
and digitally or analogically indicated in the indicator 36.
[0106] In order to measure and indicate the concentration of
N.sub.2 gas in the tire after the filling of N.sub.2 gas, the hand
valve 30 is opened and the four port valve 28 is switched into an
opening direction to discharge the gas in the outlet path into
atmosphere to an extent of replacing with a gas and then the four
port valve 28 is closed to introduce N.sub.2 gas in the tire into
the O.sub.2 sensor module 34, the measured value in the module is
stably indicated by the indicator 36 and thereafter the hand valve
30 is closed.
[0107] Even when the concentration of N.sub.2 gas is measured by
the apparatus shown in FIG. 7, the pressure inside the tire is
somewhat decreased likewise the case of FIG. 6. In this case, it is
sufficient that N.sub.2 gas is previously filled to a pressure
slightly higher than the recommended internal pressure of the tire.
Further, the sensor module 34 measuring the N.sub.2 gas
concentration and the like may directly be arranged in the outlet
path 8.
[0108] In FIG. 8 is sectionally shown the ejector shown in FIG. 7.
The compressed air is powerfully blown from a portion a of the
ejector 40 and discharged out from a portion b of the ejector 40
through a fine nozzle thereof, whereby a portion c of the ejector
40 is rendered into a vacuum state and hence air remaining in the
tire is sucked out through the discharge path 31 connected to the
portion c and the outlet path 8.
[0109] In order to more develop the effect of filling of N.sub.2
gas by sucking and discharging the remaining air in the tire
through the above manner, it is favorable that the gas filled in
the tire is sucked by the ejector 40 at least one times on the way
of filling N.sub.2 gas, whereby O.sub.2 remaining in the tire can
be decreased to a very small level to more enhance the effect by
the filling of N.sub.2 gas.
[0110] In the filling of N.sub.2 gas, the operation of sucking the
gas filled in the tire through the ejector 40 on the way of the
N.sub.2 gas filling and then filling N.sub.2 gas can be naturally
repeated several times. Even in this case, O.sub.2 remaining in the
tire is replaced with N.sub.2 gas, so that the concentration of
N.sub.2 gas in the tire can be further increased.
[0111] In the apparatus shown in FIG. 7, when N.sub.2 gas is filled
after a half of air is discharged from the inside of the tire, the
O.sub.2 concentration is about 3% after the filling into the
recommended internal pressure. On the other hand, after N.sub.2 gas
is filled into the tire assembled onto the rim so as to obtain an
internal pressure of 200 kPa without discharging air in the tire,
the filled gas is discharged toward atmosphere until the internal
pressure of the tire is 100 kPa, and then N.sub.2 gas is again
filled up to a given internal pressure, whereby the O.sub.2
concentration can be reduced to about 5% after the filling to the
internal pressure.
[0112] Although a holder is not arranged in the apparatus of FIG.
7, when a time for filling N.sub.2 gas is prolonged, it is possible
to arrange the holder in the outlet path of the above apparatus for
shortening the filling time. And also, two or more membrane modules
may be arranged in order to realize the efficient filling of
N.sub.2 gas.
[0113] In the apparatus provided with a step of discharging out air
included in the tire prior to the filling of N.sub.2 gas, the line
and devices for such a step are required and it can not be avoided
to enlarge the apparatus itself and the filling operation becomes
complicated. However, such inconveniences can be made to minimum by
adopting the construction shown in FIG. 7.
[0114] The following examples are given in illustration of the
invention and are not intended as limitations thereof.
EXAMPLES 1-3, COMPARATIVE EXAMPLE 1
[0115] N.sub.2 gas is filled into a passenger car tire having a
tire size of 195/65R15 by using N.sub.2 gas filling apparatus shown
in FIG. 1. In this case, a state of changing a gas concentration
inside the tire is measured by varying a feeding pressure of
N.sub.2 gas (300 kPa, 400 kPa, 500 kPa) to obtain results as shown
in Table 1.
1 TABLE 1 Pressure reduction A (N.sub.2 filling .fwdarw. discharge
B (N.sub.2 filling .fwdarw. discharge N.sub.2 filling .fwdarw.
N.sub.2 filling .fwdarw. N.sub.2 filling) .fwdarw. N.sub.2 filling)
Filling Filling Pressure N.sub.2 concentration Pressure N.sub.2
concentration Pressure N.sub.2 concentration Pressure N.sub.2
concentration pressure time (kPa) (%) (kPa) (%) (kPa) (%) (kPa) (%)
500 kPa 20 sec 132 90.3 102 90.5 117 96.4 120 92.5 40 sec 243 92.8
206 93.3 230 96.9 202 94.1 60 sec 330 93.8 303 94.9 263 97.2 265
94.9 400 kPa 20 sec 105 88.2 75 89.6 110 95.1 110 92.6 40 sec 197
91.0 152 92.8 190 95.9 194 94.1 60 sec 264 92.5 229 94.1 247 96.2
280 95.2 300 kPa 20 sec 85 87.3 70 87.6 89 94.5 88 91.0 40 sec 150
90.1 111 91.0 156 95.5 155 92.6 60 sec 188 91.8 188 92.4 206 95.7
210 94.1 80 sec 230 93.0 230 93.0 254 94.8
[0116] In Table 1, the term "N.sub.2 filling" is a case that
N.sub.2 gas is filled without discharging out air included in the
tire (Comparative Example 1), and the term "Pressure
reduction.fwdarw.N.sub.2 filling" is a case that N.sub.2 gas is
filled after about 30% of air included in the tire is discharged
out (Example 1), and the term "A. N.sub.2
filling.fwdarw.Discharge.fwdarw.N.sub.2 filling" is a case that
N.sub.2 gas is filled for 60 seconds without discharging air
included in the tire and gas filled in the tire is discharged out
and then N.sub.2 gas is again filled (Example 2), and the term "B.
N.sub.2 filling.fwdarw.Discharge.fwdarw.N.sub.2 filling" is a case
that N.sub.2 gas is filled for 10 seconds without discharging air
included in the tire and gas filled in the tire is discharged out
and then N.sub.2 gas is again filled (Example 3).
[0117] FIG. 9 is a graph showing a relation between pressure inside
the tire and N.sub.2 concentration based on the data of Table 1. As
seen from Table 1 and FIG. 9, in Comparative Example 1 that N.sub.2
gas is merely filled in the tire assembled onto the rim and
containing air therein (atmospheric pressure inside tire), the
N.sub.2 concentration becomes high as the filling pressure becomes
high, but the value of the N.sub.2 concentration is about 93% at
maximum, while the N.sub.2 concentration in all of Examples 1-3 is
fairly higher than that of Comparative Example 1.
EXAMPLE 4
[0118] In this example, N.sub.2 gas is filled into a large-size
tire for truck and bus having a tire size of 1000R20 by using
N.sub.2 gas filling apparatus shown in FIG. 1, wherein a feeding
pressure of compressed air is set to 1150 kPa and a pressure of
N.sub.2 gas at a downstream side of a membrane module is set to 900
kPa. Then, a time filling N.sub.2 gas up to a pressure
corresponding to a recommended internal pressure of the tire and a
gas concentration in the tire at the recommended internal pressure
are measured.
[0119] When about a half of air is discharged from the inside of
the tire and then N.sub.2 gas is filled up to the recommended
internal pressure, the filling time is 8 minutes and the
concentration of N.sub.2 gas in the tire is 97.5%.
[0120] When an operation that N.sub.2 gas is filled without
discharging air included in the tire and a gas filled in the tire
is discharged and then N.sub.2 gas is again filled up to the
recommended internal pressure is repeated three times, the filling
time is 18 minutes and the concentration of N.sub.2 gas in the tire
is 98.5%.
EXAMPLES 5-7, COMPARATIVE EXAMPLE 2
[0121] In this example, N.sub.2 gas is filled into a passenger car
tire (PS) having a tire size of 195/65R15 (recommended internal
pressure: 240 kPa) or a large size tire for truck and bus (TB)
having a tire size of 1000R20 (recommended internal pressure: 725
kPa) by using N.sub.2 gas filling apparatus shown in FIG. 3,
wherein a feeding pressure of compressed air is set to 520 kPa (PS)
or 1030 kPa (TB) and a pressure of N.sub.2 gas at a downstream side
of a membrane module is set to 500 kPa (PS) or 1000 kPa (TB),
during which the filling operability and concentration of N.sub.2
gas in the tire are measured.
[0122] When N.sub.2 gas is filled without discharging out air
included in the tire (Comparative Example 2), the filling time is
40 seconds in case of PS and 6 minutes in case of TB, and the
concentration of N.sub.2 gas in the tire is 93% in case of PS and
95% in case of TB.
[0123] When about 30% of air included in the tire is discharged out
and then N.sub.2 gas is filled (Example 5), the filling time is 50
seconds in case of PS and 400 seconds in case of TB, and the
concentration of N.sub.2 gas in the tire is 94% in case of PS and
96% in case of TB.
[0124] When N.sub.2 gas is filled for 40 seconds (PS) or 360
seconds (TB) without discharging air included in the tire and a gas
filled in the tire is discharged and then N.sub.2 gas is again
filled (Example 6), the filling time is 80 seconds in case of PS
and 640 seconds in case of TB, and the concentration Of N.sub.2 gas
in the tire is 97% incase of PS and 98.5% in case of TB.
[0125] When N.sub.2 gas is filled for 10 seconds without
discharging air included in the tire and a gas filled in the tire
is discharged and then N.sub.2 gas is again filled (Example 7), the
filling time is 60 seconds in case of PS and 480 seconds in case of
TB, and the concentration Of N.sub.2 gas in the tire is 95% incase
of PS and 97% in case of TB.
[0126] As mentioned above, according to the invention, it is
possible to efficiently fill N.sub.2 gas into a tire assembled onto
a rim irrespectively of the kind of the tires having different
recommended internal pressures such as passenger car tire, truck
tire, bus tire and the like and also the ratio of air (O.sub.2 gas)
remaining in the tire can considerably be decreased, so that merits
by the filling of N.sub.2 gas can be utilized at maximum.
[0127] And also, according to the invention, air remaining in the
tire can be sucked and discharged out by utilizing the compressed
air used in the formation of N.sub.2 gas, so that the filling
operation of N.sub.2 gas is very simple and it is enough to add
only a line passing the compressed air to the filling apparatus
without enlarging the apparatus itself.
[0128] Furthermore, according to the invention, the change of
N.sub.2 gas concentration during the filling of N.sub.2 gas into
the tire or the N.sub.2 gas concentration in the tire after the
filling is visually confirmed, so that the reliability to the users
can considerably be enhanced.
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