U.S. patent application number 10/023185 was filed with the patent office on 2002-07-11 for safety insert generating a transverse vibrating signal and device for sensing the tire bearing on the insert.
Invention is credited to Dufournier, Arnaud, Hottebart, Francois.
Application Number | 20020088518 10/023185 |
Document ID | / |
Family ID | 27253317 |
Filed Date | 2002-07-11 |
United States Patent
Application |
20020088518 |
Kind Code |
A1 |
Dufournier, Arnaud ; et
al. |
July 11, 2002 |
Safety insert generating a transverse vibrating signal and device
for sensing the tire bearing on the insert
Abstract
A safety insert designed to be mounted in an assembly comprising
a tire and a rim of a vehicle and device for detecting the bearing
of the tire on an insert, so that the insert generates signals
oriented parallel to the axis of rotation of the tire and rim
assembly and so that the device detects and analyzes the vibrating
signals of the chassis of the vehicle.
Inventors: |
Dufournier, Arnaud;
(Clermont-Ferrand, FR) ; Hottebart, Francois;
(Royat, FR) |
Correspondence
Address: |
BAKER & BOTTS
30 ROCKEFELLER PLAZA
NEW YORK
NY
10112
|
Family ID: |
27253317 |
Appl. No.: |
10/023185 |
Filed: |
December 18, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10023185 |
Dec 18, 2001 |
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09418283 |
Oct 14, 1999 |
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09418283 |
Oct 14, 1999 |
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PCT/EP98/02251 |
Apr 17, 1998 |
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Current U.S.
Class: |
152/154.2 ;
152/152; 73/146 |
Current CPC
Class: |
B60C 2019/006 20130101;
B60C 23/0469 20130101; B60C 17/04 20130101; B60C 17/06 20130101;
Y10T 152/10027 20150115; B60C 23/063 20130101; Y10T 152/10009
20150115 |
Class at
Publication: |
152/154.2 ;
73/146; 152/152 |
International
Class: |
G01M 017/02 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 18, 1997 |
FR |
97/05243 |
Jan 30, 1998 |
FR |
98/01385 |
Mar 3, 1998 |
FR |
98/02809 |
Claims
We claim:
1. A safety insert designed to be mounted in an assembly comprising
a tire and a rim of a vehicle and radially on the outside of the
rim, said insert having a radially outer bearing surface which
defines a radial bearing for the crown of the tire when said tire
is deflated and means for generating vibrating warning signals on a
run-flat condition, characterized in that said means generate
signals oriented parallel to the axis of rotation of the tire and
rim assembly.
2. A safety insert according to claim 1, in which the bearing
surface of the insert presents a variation of transverse position
according to the azimuth of said bearing.
3. A safety insert according to claim 1, in which the bearing
surface of the insert contains straight ribs, the circumferential
orientation of which varies with their azimuth.
4. A safety insert according to claim 1, in which the bearing
surface of the insert contains elements generating a transverse
stress upon their radial compression.
5. A safety insert according to claim 4, in which the elements
comprise ribs or incisions whose inclinations relative to a
longitudinal plane vary with their azimuth.
6. A safety insert according to claim 4, in which the bearing
surface has an appreciably constant rolling radius under
bearing.
7. A safety insert according to claim 1, in which the bearing
surface presents at least two axially adjacent zones, the zone
intended to be placed outward from the vehicle not containing means
for generating signals oriented parallel to the axis of rotation of
the tire, and rim assembly.
8. A safety insert according to claim 1, including means for
generating vertical signals.
9. A safety insert according to claim 1, in which the bearing
surface contains an active zone of generation of signals, such that
said signals present a maximum preceded and followed by a minimum
in the opposite direction.
10. A safety insert according to claim 9, in which said active zone
lies between 1/4 and 1/2 of the circumference of said insert.
11. A safety insert according to claim 9, in which the absolute
value of the minima of the signal generated lies between 1/4 and
3/4 of the absolute value of the maximum.
12. A device for detecting the bearing of a tire of a vehicle,
equipped with a plurality of tire, rim and safety insert
assemblies, the insert of each assembly being mounted between the
rim and the radially inner face of the tire tread, on the
corresponding safety insert, each assembly being capable of
triggering the emission of a vibrating signal when the tire comes
in contact with the insert after a pressure loss in the tire,
comprising means of detection and treatment of said vibrating
signal, including a single sensor capable of being mounted on the
vehicle and sensitive to the signals emitted by each of the said
assemblies, when the corresponding tire comes in contact with the
respective insert, and an indicator capable of signaling to the
occupant of the vehicle a run-flat condition in response to a
signal picked up by said sensor.
13. A device according to claim 12, in which the vibrating signal
is maintained by running flat.
14. A device according to claim 12, including a pressure-sensitive
generator and in which the vibrating signal is a signal emitted by
a pressure-sensitive generator.
15. A device according to claim 12, in which the vibrating signal
is an acoustic signal.
16. A device for detection of bearing of a tire of a vehicle,
equipped with a plurality of tire, rim and safety insert assemblies
in which the safety inserts are mounted between the rim and the
radially inner face of the tire tread, on the corresponding safety
insert, each assembly being capable of transmitting a
characteristic vibration to the chassis of the vehicle in response
to the bearing of one of the tires on the corresponding safety
insert as a result of a pressure loss in the tire, comprising:
means of detection and treatment of such predetermined
characteristic mechanical vibration of the chassis of the vehicle;
and means of transmission of an alarm.
17. A device according to claim 16, in which the vehicle has at
least two axles and the means of detection of a predetermined
characteristic vibration of the chassis of the vehicle comprise one
and not more than one sensor per axle of said vehicle.
18. A device according to claim 17, in which the means of detection
of a predetermined vibration of the chassis of the vehicle comprise
a single sensor connected to the vehicle.
19. A device according to claim 18, in which the means of detection
of a predetermined characteristic vibration of the vehicle comprise
a single sensor rigidly connected to the chassis of the
vehicle.
20. A device according to claim 16, in which the characteristic
vibration transmitted to the chassis by the tire, rim and insert
assembly includes a component oriented parallel to the axis of
rotation of said assembly.
21. A device according to claim 12 or claim 16, in which the
treatment means calculate a first characteristic magnitude in at
least a first given frequency band, calculate a criterion C
corresponding to a given combination of the preceding first
characteristic magnitude or magnitudes, compare that criterion C to
a given threshold and trip an alarm when the result of the
comparison follows a given ratio.
22. A device according to claim 21, in which, for each of the axles
of the vehicle, the treatment means calculate a first
characteristic magnitude in at least a first frequency band
specific to said axle of the vehicle.
23. A device according to claim 22, in which the treatment means
calculate a criterion C corresponding to a weighted value of said
first characteristic magnitudes of said first frequency bands
specific to said axles of the vehicle.
24. A device according to claim 21, in which the first frequency
band or bands lie between 20 and 100 Hz.
25. A device according to claim 21, in which the treatment means
further determine the frequency of rotation of the tire and in
which said first frequency band or bands are narrow frequency
bands, each centered on a multiple frequency of said frequency of
rotation of the tire.
26. A device according to claim 25, in which said first frequency
band or bands lie between 10 and 200 Hz.
27. A device according to claim 21, in which the means of treatment
of the vibrations of the chassis further calculate a second
characteristic magnitude in at least a given second frequency band,
so that, in said second band, said vibrations are appreciably
independent of bearing of the tire on its safety insert and so that
the alarm tripping threshold is a function of said second
characteristic magnitude.
28. A device according to claim 27, in which said second frequency
band lies between 3 and 7 hz.
29. A device according to claim 27, in which said second frequency
band lies between 100 and 200 hz.
30. A device according to claim 27, in which said second bands are
situated outside the multiple frequencies of the frequency of
rotation of the tire.
31. A device according to claim 21, in which the characteristic
magnitude measured is the vibrational energy of the signals
expressed by the rms value.
32. A device according to one of claims 12 or 16, in which the
treatment means do not transmit any alarm when the speed of the
vehicle is below a given threshold.
33. A tire designed to equip a tire, wheel and safety insert
assembly in which the safety insert is mounted between the rim and
the radially inner face of the tire tread, characterized in that
said tire is equipped with means capable of generating a vibrating
signal when said tire comes in contact with a corresponding insert
following a pressure loss in said tire.
Description
[0001] This is a continuation of PCT EP 98/0225 1, filed Apr. 17,
1998.
BACKGROUND OF THE INVENTION
[0002] The invention concerns the use of tires equipped with a
safety insert and, in particular, detection of the bearing of a
tire on the safety insert. It proposes an insert which warns the
driver as soon as the tire is bearing on it after a flat or in case
of substantial pressure loss, as well as a device for sensing the
tire bearing on the insert, which can be combined with the insert
proposed.
[0003] The function of these safety inserts, which are generally
mounted on the rim inside the tire, is to bear the load in case of
failure of the tire.
[0004] Bearing of the tire on the safety insert is accompanied by a
more or less marked deterioration of its performances, which can
fail to be perceptible to the driver through the behavior of the
vehicle and the discomfort of the passenger. Furthermore, the
operating lifetime of these inserts is limited. It is therefore
essential, for the driver's safety, for the driver to be warned as
soon as a tire is bearing on its safety insert, so that the driver
can follow the manufacturer's instructions.
[0005] Several safety inserts incorporating means for so warning
the driver have previously been proposed.
[0006] U.S. Pat. No. 4,262,724 discloses a safety insert intended
to be mounted in an assembly comprising a tire and a rim and
radially on the outside of the rim. This insert has a radially
outer surface which defines a radial bearing for the crown of the
tire, when the tire is deflated, as well as means for generating
vibrating warning signals on running flat. These means can be a
variation of the rolling radius under bearing of the insert between
a minimum radius and a maximum radius in order to create a rolling
vibration or one or more bumps. All the vibrating warning signals
generated by these means are oriented in the plane of the tire and
rim assembly and, more specifically, in a roughly vertical
direction.
[0007] These solutions pose several problems. In addition to marked
discomfort for passengers of the vehicle, they can markedly degrade
the performance of the tire and rim assembly concerned,
particularly on acceleration and braking. Thus, all one can do is
avoid instantaneous stoppage of the vehicle in case of failure of
the tire. On the other hand, when it is desired to use the vehicle,
even at limited speed, over long distances, the warning transmitted
by the insert has to be compatible with driving safety, not
detrimental to the mechanics, while remaining perfectly noticeable
to the driver either directly or through a suitable detection
device.
[0008] Patent application WO 94/03338 also proposes a device for
the detection of the bearing of a tire on a safety insert. This
device comprises a wheel accelerometer, placed on one of the wheel
suspension elements and measuring vertical accelerations. The
accelerometers are connected to a central processing unit. The
analysis is based on detection of the appearance of a resonance
mode characteristic of the run-flat condition.
SUMMARY OF THE INVENTION
[0009] The object of the invention is a safety insert which warns
the driver, either directly or indirectly, upon bearing of the tire
over a very wide range of speeds of the vehicle, while remaining
tolerable to the driver and the mechanics within the speed
limits.
[0010] The invention also concerns a device for detection of the
bearing of a tire on its safety insert, which can, notably,
cooperate with the safety insert according to the invention.
[0011] "Vehicle" is understood below to be a self-contained rolling
unit, passenger car, truck, tractor-trailer, motorcycle, etc.
[0012] "Rib" refers to an element situated on the radially outer
surface of a safety insert, of elongated shape, of roughly
circumferential orientation and the radial height of which is less
than or equal to the axial width: the ribs are "straight" when
their axial section is rectangular and "inclined" when their axial
section is in the shape of a parallelogram.
[0013] "Incision" describes a similar element whose radial height
is greater than the axial width.
[0014] The safety insert according to the invention, intended to be
mounted in an assembly comprising a tire and a rim of a vehicle and
radially on the outside of the rim, presents a radially outer
surface which defines a radial bearing for the crown of the tire
when it is deflated and means for generating vibrating warning
signals on a run-flat condition. The said insert is characterized
in that said means generate signals oriented parallel to the axis
of rotation of the tire and rim assembly.
[0015] Said insert has two major advantages: the vibrating signals
generated in the transverse direction are much more easily
transmitted to the chassis and to the driver than similar
vertically oriented signals. This is due to the excellent filtering
carried out by the vehicle suspensions in the vertical direction in
order to preserve the comfort of the passengers of the vehicle,
while any transmission of stresses in the transverse direction is
almost direct, with few filtering elements. On the other hand,
those transverse vibrating signals degrade the performance of the
tire and rim assembly in a straight line markedly less than those
vertically oriented.
[0016] In a first embodiment of the invention, the bearing surface
of the insert presents a variation of transverse direction
according to its azimuth.
[0017] In a second embodiment, the bearing surface of the insert
presents straight ribs, the circumferential orientation of which
varies with their azimuth.
[0018] And in a third embodiment, the bearing surface of the insert
presents elements generating a transverse stress on their radial
compression.
[0019] This embodiment is particularly flexible. It is, in fact,
possible to use inclined ribs or incisions relative to a
longitudinal plane in variable manner according to their
azimuth.
[0020] In a preferred variant, the safety insert according to the
invention has a bearing surface with at least two axially adjacent
zones, the zone intended to be placed outward from the vehicle not
containing means for generating signals oriented parallel to the
axis of rotation of the tire and rim assembly.
[0021] The latter solution has the advantage of preserving
excellent turn performance of the tire and rim assembly upon
running on a safety insert. In fact, on a turn, the tires placed
outward from the turn are more loaded and usually take a marked
counter-camber angle. Under such conditions, it is the "inactive"
bearing zone (that is, not containing means for generating signals
oriented parallel to the axis of rotation of the tire and rim
assembly) which supports the bulk of the tire load without
generating specific transverse vibrating signals. On the other
hand, on a straight run, the tires have a much smaller camber angle
and, the bearing zone containing means for generating transverse
vibrating signals, the "active" zone is then stressed.
[0022] The shape of the signal generated by the safety insert is
also very important. The safety insert according to the invention
preferably comprises a bearing surface with an active
signal-generating zone, so that said signals present a maximum
preceded and followed by a minimum in the opposite direction.
[0023] The active zone advantageously ranges between 1/4 and 1/2
the circumference of said insert and the absolute value of the
minima of the signal generated ranges between 1/4 and 3/4 the
absolute value of the maximum.
[0024] Such generated signals have the advantage of giving a
spectrum of vibrations transmitted to the chassis of the vehicle on
a run-flat condition in a well defined frequency band which favors
precise and reliable detection.
[0025] The invention also concerns a first device for detection of
the bearing of a tire of a vehicle, equipped with a plurality of
tire, rim and safety insert assemblies mounted between the rim and
the radially inner face of the tire tread, on the corresponding
safety insert, each assembly being capable of triggering the
emission of a vibrating signal, when the tire comes in contact with
the insert after a pressure loss in the tire. Said detection device
comprises means of detection and treatment of said vibrating
signal, containing a single sensor capable of being mounted on the
vehicle and sensitive to the signals emitted by each of the
assemblies, when the corresponding tire comes in contact with the
respective insert, and an indicator capable of signaling to the
occupant of the vehicle a run-flat condition in response to a
signal picked up by said sensor.
[0026] The characteristic vibrating signal is preferably maintained
by the run-flat condition and can be emitted by a
pressure-sensitive generator. Such a generator placed in the insert
or on its surface is sensitive to any stress associated with the
bearing of the tire tread on the insert and emits a signal,
acoustic, for example, when that stress exceeds a given threshold.
The acoustic signal can be easily picked up by a single receiver
placed in the passenger space of the vehicle, connected to an
indicator capable of warning the occupant of the vehicle of the
run-flat condition.
[0027] The invention also concerns a second device for detection of
bearing of a tire of a vehicle, equipped with a plurality of tire,
rim and safety insert assemblies mounted between the rim and the
radially inner face of the tire tread, on the corresponding safety
insert, each assembly being capable of transmitting a
characteristic vibration to the chassis of the vehicle in response
to the bearing of one of the tires on the corresponding safety
insert as a result of a pressure loss in the tire. This device
comprises:
[0028] means of detection and treatment of such predetermined
characteristic mechanical vibration of the chassis of the vehicle;
and
[0029] means of transmission of an alarm.
[0030] This device presents the feature, by comparison with known
devices, of making an analysis of the vibrations of the chassis of
the vehicle instead of the suspension members.
[0031] As in the insert previously described, said device can
preferably use direct paths of transmission of vibrations between
the wheels and the chassis, in addition to vertical directions.
Consequently, said device can be much more selective and sensitive
than the existing devices and may have only one sensor rigidly
connected to one of the parts of the chassis.
[0032] The device according to the invention is particularly
well-suited to detection of bearing of a tire on a safety insert
according to the invention, but it can also be used with any other
insert, with or without vibrating means for alerting the driver to
the bearing problem. In such case, it may be necessary to use two
or more sensors measuring accelerations instead of only one. Each
sensor is then preferably connected to one of the axles of the
vehicle.
[0033] The means of treating vibrations of the chassis calculate a
first characteristic magnitude in at least one given frequency
band, they calculate a criterion C corresponding to a given
combination of the preceding first characteristic magnitude or
magnitudes, they compare that criterion C to a given threshold and
they trip an alarm when the result of the comparison follows a
given ratio.
[0034] Preferably, for each of the axles of the vehicle, the
treatment means calculate a first characteristic magnitude in at
least a first frequency band specific to the axle of the vehicle
and calculate a criterion C corresponding to a weighted value of
these first characteristic magnitudes.
[0035] The means of treating the vibrations of the chassis can also
calculate, in addition, a second characteristic magnitude in a
given second frequency band, so that, in said second band, said
vibrations are appreciably independent of the bearing of the tire
on its safety insert and deduce therefrom a criterion C
corresponding to a value normed by that second characteristic
magnitude of the first characteristic magnitudes, weighted or
not.
[0036] According to a preferred embodiment, the treatment means
further determine the frequency of rotation of the tire and said
first frequency band or bands are narrow frequency bands, each
centered on a multiple frequency of said tire rotation frequency.
Those first frequency bands preferably range between 10 and 200
Hz.
[0037] The treatment centered on multiple frequencies of the tire
rotation frequency very appreciably improves the sensitivity of
bearing detection.
[0038] The characteristic magnitude calculated can be the rms
values of the signals.
[0039] The invention also concerns a tire designed to equip a tire,
wheel and safety insert assembly mounted between the rim and the
radially inner face of the tire tread, characterized in that said
tire is equipped with means capable of generating a vibrating
signal, when said tire comes in contact with a corresponding insert
following a pressure loss in said tire. These means can, for
example, be a pressure-sensitive generator adhered to the inner
surface of the tire.
DESCRIPTION OF THE DRAWINGS
[0040] Several embodiments of the invention are now described by
means of the attached drawing in which:
[0041] FIG. 1 shows, in meridian section, a tire and rim assembly
equipped with a safety insert;
[0042] FIG. 2 shows, in meridian section, a first embodiment of a
safety insert according to the invention;
[0043] FIG. 3 shows, in meridian section, a second embodiment;
[0044] FIG. 4 shows, in meridian section, a third embodiment;
[0045] FIG. 5 shows, in cross section, a safety insert with two
axially adjacent zones;
[0046] FIG. 6 shows schematically a preferential shape of signals
generated by the insert on rolling;
[0047] FIG. 7 is a schematic diagram of the detection device
according to the invention;
[0048] FIG. 8 presents two spectra of measurement of appreciably
horizontal accelerations according to frequency with and without
bearing registered on an ordinary road;
[0049] FIG. 9 illustrates an example of evolution with time upon
rolling with or without bearing of the resultant magnitude
calculated by the microcontroller of the device;
[0050] FIGS. 10a and 10b show, in meridian section, two variant
tire and rim assemblies equipped with a safety insert.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0051] FIG. 1 shows a wheel rim 1 equipped with an annular safety
insert 2 resting on the bearing 6 of the rim 1. The particular
geometry of said wheel rim 1 is described in French patent
application No. 2,713,558. It provides two bead seats of different
diameters and is particularly well suited for the easy placement of
that safety insert 2. This assembly makes rolling possible in spite
of a large pressure drop in the tire 3. In case of such rolling,
the inside of the deformed tire rubs on the outer surface of the
insert, producing heating which limits the available radius of
action; it is therefore important for the driver to be informed as
soon as a tire rests on its inset 2.
[0052] For this purpose, a safety insert according to the invention
is used as insert, containing means for generating transverse
vibrating warning signals.
[0053] A first embodiment of such an insert is shown in FIG. 2.
This insert 9 has a bearing surface 10 which is axially shifted
according to its azimuth. Consequently, upon a run-flat condition
of said surface 10 against that of the crown of the tire, the tire,
rim and insert assembly will produce on each turn of the wheel a
lateral thrust oscillation that the driver or a detection device
will perceive.
[0054] FIG. 3 shows another embodiment. The bearing surface 13 of
the insert 12 is formed by incisions 14 inclined relative to a
transverse plane of the insert and the inclination of which varies
with their azimuth. In the example shown, the inclination is
diametrically opposite and the course of the inclination is
appreciably sinusoidal. These incisions therefore produce, on
loading, transverse stresses of the same frequency as the turn of
the wheel, again easily perceptible to the driver of the vehicle,
whether directly or not.
[0055] It is also possible to use ribs or preferably relatively
wide ribs arranged adjacent to incisions of similar or greater
radial height. In the latter case, it is advantageous to so design
the rigidity and geometry of said incisions and strips that the
radius of rolling of the insert remains constant on a run-flat
condition.
[0056] FIG. 4 shows a safety insert 15 containing two axially
adjacent zones A and B. Zone B, arranged on the side intended to be
placed outward from the vehicle, does not contain means for
generating signals oriented parallel to the axis of rotation of the
tire and rim assembly. Said zone is thus inactive when zone A,
arranged toward the vehicle, contains incisions inclined to
generate transverse vibrating signals. Said insert 15 makes it
possible to maintain excellent turn performance, for it is then the
roughly cylindrical zone B which supports most of the load of
bearing of the crown of the tire, by reason of the wide angle of
counter-camber taken by the latter. In a straight line, the
operation of the insert 15 is similar to that of FIGS. 2 and 3.
[0057] Such an insert can also advantageously have a slight conical
zone B with its minimum diameter on the outer side of the insert,
in order to fit well the counter-camber angle taken by the tire and
wheel on turning. There can also be an insert containing two
adjacent cylindrical or conical zones on the outside of a central
active zone.
[0058] FIG. 5 shows an insert 16 containing, in addition to
incisions of inclination varying with the azimuth, two radial bumps
17 and 18 created by giving the incisions a height varying with the
azimuth, which result in a vertical vibratory excitation. The
circle L corresponds to the outside of the insert bearing surface
and the oval M corresponds to the casing at the base of the
incisions. The incisions in the present example thus have zero
height at the two crowns of bumps 17 and 18. It has, in fact, been
observed that such an insert 16, coupling generations of transverse
and vertical vibrations, appreciably increases the total energy
transmitted in the vehicle.
[0059] FIG. 6a shows a preferred shape of the signal generated by a
safety insert according to the invention. Said signal differs from
zero only within a zone limited to approximately 1/3 the
circumference of the insert. It comprises a first minimum
F.sub.Ymin followed by a maximum F.sub.Ymax of opposite direction
and followed, finally, by a second minimum. The two minima can have
the same amplitude ranging between 1/5 and 1/2 of F.sub.Ymax.
[0060] The safety inserts previously described can easily generate
signals similar to those of FIG. 6. It is sufficient for the means
used to generate the Y signals to vary similarly. In the case of
insert 9, the lateral position of the bearing surface 10 can follow
a course corresponding to that of a or b of FIG. 6. By reason of
the weighting due to the finite length of the area of contact
between the tire and the bearing surface of the insert, a variation
similar to that of b in FIG. 6 will result in a course of the
signal generated close to the shape of curve a. In the case of
insert 12 of FIG. 3, it is the orientation of the ribs or incisions
which must follow a course corresponding to curves a or b in FIG.
6.
[0061] In the usual manner, in order to limit heating of the insert
and tire on run-flat condition, a lubricant is introduced in the
inner cavity of the tire and, in particular, on the bearing surface
of the insert. To improve adherence between the bearing surface of
the insert and the crown of the tire, it is advantageous to arrange
on the bearing surface incisions of roughly circumferential
orientation, which will play the same role as the incisions of the
tire sculptures in order to remove water in the area of contact
between the tire and the road.
[0062] The safety inserts according to the invention can generate
signals of great enough intensity to be perceived by the driver of
a vehicle. However, to preserve the comfort of the passengers of
the vehicle, it is also possible to use these inserts with a
bearing detector which will now be described.
[0063] FIG. 7 schematically presents the detector according to the
invention, intended to be used with a two-axle passenger car, for
example, a Renault Twingo. Said device 20 includes a sensor 21; a
series of bandpass filters 22, 23, 24; three analog extractors 25,
26, 27 of the rms value of the signals; a microcontroller 28 and an
indicator 29. The assembly is placed in a single box designed to be
rigidly connected to one of the parts of the chassis of the
vehicle. The sensor 21 is preferably a unidirectional accelerometer
so arranged in the vehicle that it measures the accelerations in a
plane embracing the longitudinal and transverse axes of the
vehicle. The signals are then filtered by a series of bandpass
filters placed in parallel. Filter 22 eliminates the signals
outside a band A adapted to the rear axle of the vehicle, in the
order of 20 to 50 Hz. Filter 23 eliminates the signals outside a
band B adapted to the front axle of the vehicle, in the order of 50
to 80 Hz and filter 24 lets pass the signals lying in a band E, in
which the signals are appreciably independent of the bearing of a
tire on its safety insert, in the order of 100 to 200 Hz or
preferably of 100 to 160 Hz. These three frequency bands can,
notably, vary with the type of safety insert used as well as with
the vehicle chosen.
[0064] Extractors 25, 26 and 27 obtain rms values of the signals
transmitted respectively by bandpass filters 22, 23 and 24. The
microcontroller 28 digitizes the signals in the digital analog
converter (A/N) 30. Element 31 of the microcontroller 28 calculates
a criterion C; it can notably produce a weighted total of the rms
values of the signals of bands A and B and norm that total by the
rms value of the signals of band E.
[0065] The vibrational energy lying in band E depends on the type
of road on which the vehicle runs. The normalization obtained
appreciably improves the sensitivity of the detector by reducing
the number of false alarms. Said band E can also lie in a very low
frequency band, in the order of 3 to 7 Hz, for example.
[0066] Criterion C is then compared to a programmable given
threshold 33 in the comparator 32 and an alarm is set off by means
of the indicator 29 when C is higher than the threshold.
[0067] FIG. 9 presents the course of criterion C when the four
tires of the Renault Twingo are correctly inflated (zone A) and
when one of those tires is deflated, which results in the bearing
of that tire on its safety insert (zone B). Curve 1 shows the rough
course of C and curve 2 shows the result after comparison with the
threshold. Said result is zero when C is below the threshold and is
1 when C is above the threshold.
[0068] The indicator transmits an alarm to the driver when the
result of comparison is 1. Said indicator can be accompanied by a
buzzer.
[0069] In the case of a heavy-load vehicle, as many frequency bands
can be adopted as there are axles in the vehicle, tractor or
trailer. There are, of course, also as many sensors as there are
vehicles.
[0070] When the speed of the vehicle diminishes and approaches
zero, the vibrational energy of the different signals diminishes
and becomes more and more sensitive to local disturbances.
Consequently, tripping of the alarms can be stopped when the speed
of the vehicle is below a given threshold, for example, 7 km/h.
[0071] FIG. 8 shows an example of a spectrum of vibrations measured
by the sensor 21 upon rolling with the Renault Twingo. A first
curve corresponds to the case in which the four tires are correctly
inflated. A peak is usually observed at the low frequencies, toward
9 Hz; that peak corresponds to the first harmonic of the turn of
the wheel.
[0072] A second curve corresponds to the case in which a tire on
the front axle is deflated and bearing on its safety insert. Said
curve presents a strong spectral response between 50 and 75 Hz with
peaks linked to the different harmonics of the turn of the wheel.
In this case, the 50-80 Hz band B has been chosen as characteristic
frequency band of that front axle.
[0073] The third curve illustrates the case in which one of the
tires of the rear axle of the Renault Twingo is bearing on its
safety insert. Two notable peaks are observed toward 20 and 40 Hz.
The 20-50 Hz band A is then chosen as characteristic band of the
rear axle.
[0074] It is also observed in FIG. 8 that, in frequencies below 7
Hz, or between 100 and 200 Hz, there is practically no noticeable
change in the curves whether or not running flat. Consequently, in
order to take into account the vibrational energy due to the type
of road on which the vehicle runs, the measurements are normed in
the preceding characteristic frequency bands by measurement of the
rms value in a band E such as 100-160 Hz or 3-7 Hz. This makes it
possible to rely on the quality of the bearing detection. When the
speed of the vehicle diminishes, so that the first harmonic of the
turn of the wheel becomes around 7 Hz, in order to avoid
disturbances, the transmission of alarms is inhibited.
[0075] To have a single criterion of bearing detection and taking
into account the notable energy differences between the
measurements upon bearing of a front or rear tire on its insert,
the measurements can be weighted in order to obtain a
characteristic magnitude roughly of the same value, regardless of
the axle of the tire bearing on its insert. This is what is done
for the curve presented in FIG. 9.
[0076] Curves 8 and 9 are obtained with a safety insert generating
a transverse signal over one-third the circumference of the insert
and varying between zero and F.sub.Ymax. This generated signal has
a broader spectrum than that of FIG. 6. The detector used has a
single unidirectional sensor rigidly connected to the chassis of
the vehicle placed with a transverse orientation.
[0077] The signal shape presented in FIG. 6 has the advantage of
well delimiting in frequency the signals transmitted to the chassis
of the vehicle and of concentrating those signals in mainly a
single frequency band. Said band is defined to embrace, whatever
the speed of the vehicle beyond a few kilometers per hour, the
characteristic frequency bands of each of the axles of the vehicle.
This makes it possible to rely on the quality of detection and to
limit false alarms. This also makes it possible to use the energy
transmitted to best advantage without degrading the comfort of the
vehicle. The F.sub.Ymax values of those signals can thus be
reduced.
[0078] According to another embodiment, the means of treatment:
[0079] determine the frequency of rotation of the tires of the
vehicle;
[0080] calculate the frequencies of n first harmonics of the
frequency of rotation of the tires (turn of the wheel);
[0081] calculate the vibrational energies of the n narrow frequency
bands centered on the n first harmonics;
[0082] figure, if necessary, the total of the three maximum
energies in order to obtain a criterion C;
[0083] compare that criterion C to a function threshold of speed
and unevennesses of the road; and
[0084] trip an alarm if C is higher than that threshold.
[0085] The speed information can be obtained from the tachometer of
the vehicle; it can also be deduced from the signals registered by
determining the frequency position of the first peak (see FIG. 8).
"Narrow band" of frequency is understood to be a band of width
below 5 Hz.
[0086] As can be seen on the curves of FIG. 8, the frequencies
corresponding to the harmonics of the first peak (turn of the
wheel) are also spectrum peaks. Consequently, analyzing the
harmonics of the turn of the wheel makes it possible to improve
very appreciably the detection of bearing of a tire on its safety
insert.
[0087] To facilitate calculations, they can be limited to a few
harmonics, from 5 to 11, for example, from harmonic 2 to harmonic 6
or 12, depending on the vehicles. The corresponding frequencies,
for a wide range of speeds of the vehicle, are found in the
frequency band where the vibrations of the insert can be
transmitted to the chassis of the vehicle by the different
suspension elements. Said band usually lies between 10 and 200
Hz.
[0088] As it is always possible for one or more peaks to be
disturbed by other sources, such as vibrations of the engine, it is
useful to analyze these harmonics to calculate the vibrational
energies of the narrow bands centered on them and to total, for
example, the three maximum energy bands in order to calculate
criterion C.
[0089] As previously, it is useful to determine the vibrational
energy in at least one frequency band, in which the spectrum
measured is appreciably independent of bearing, in order to be able
to estimate what might be due to the unevennesses of the road
traveled. In this method of analysis, said second band should not
contain the harmonics of the turn of the wheel.
[0090] Criterion C is a function of speed of the vehicle; it can be
compared to a function threshold of speed and the vibrational
energy level due to the road and, as previously, trip an alarm when
that threshold is crossed.
[0091] To avoid false alarms, provision is made for two tests of
nontripping of the alarm. The first is linked to the speed of the
vehicle; it provides for neutralization of the alarm when the speed
is below a given threshold, for example, 25 km/h. Determination of
the energy due to unevennesses of the road makes it possible to
introduce the second test of nontripping of the alarm, when that
energy linked to the road exceeds a given value. In this case, that
corresponds to rolling over a very bad road and the energy due to
the unevennesses of the road is such that it renders bearing
detection too haphazard.
[0092] The safety inserts according to the invention can be made
essentially of very rigid elastomeric material. They can also be
made of any other material, such as a loaded or unloaded
plastic.
[0093] The invention also concerns another device for the detection
of bearing of a tire on its safety insert by reason of a pressure
loss. Said device uses tire, rim and safety insert assemblies
capable of triggering the emission of a vibrating signal when the
tire comes in contact with the insert after a pressure loss in the
tire. Such a device uses, for example, a generator 50 sensitive to
the pressure emitting a predetermined radio signal when the bearing
and the inner surface of the tire are in contact. Said generator 50
can be adhered to the inner surface of the tire, as in FIG. 10b, or
to the outer surface of an insert, as in FIG. 10a.
[0094] The device comprises such a tire, rim and insert assembly
and a single receiver of the signals emitted by the generators 50,
as well as an indicator capable of warning the occupant of the
vehicle of the bearing condition.
* * * * *