U.S. patent application number 16/334833 was filed with the patent office on 2019-11-07 for method for assisting with inflating the tires of a vehicle.
The applicant listed for this patent is Continental Automotive France, Continental Automotive GmbH. Invention is credited to Stephane Billy, Sylvain Godet, Sebastien Kessler.
Application Number | 20190337341 16/334833 |
Document ID | / |
Family ID | 57348992 |
Filed Date | 2019-11-07 |
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United States Patent
Application |
20190337341 |
Kind Code |
A1 |
Godet; Sylvain ; et
al. |
November 7, 2019 |
METHOD FOR ASSISTING WITH INFLATING THE TIRES OF A VEHICLE
Abstract
A self-adaptive method for assisting in the inflation of tires
of a vehicle that is stationary in an immobilization mode, the
method including continuously measuring at least the pressure of
each tire by way of a wheel unit, transmitting signals on the state
of the tires between each wheel unit and a central unit, these
signals being transmitted by each wheel unit through
frequency-shift keying between two first predetermined frequencies
defining a first frequency band. In a immobilization mode, each
wheel unit is reprogrammed such that it transmits, to the central
unit, first and second frequency-shift keyed signals respectively
with first and second frequency bands, the second band being wider
than the first band.
Inventors: |
Godet; Sylvain;
(Saint-Cezert, FR) ; Billy; Stephane; (Grenade,
FR) ; Kessler; Sebastien; (Dremil-Lafage,
FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Continental Automotive France
Continental Automotive GmbH |
Toulouse
Hannover |
|
FR
DE |
|
|
Family ID: |
57348992 |
Appl. No.: |
16/334833 |
Filed: |
September 18, 2017 |
PCT Filed: |
September 18, 2017 |
PCT NO: |
PCT/FR2017/052488 |
371 Date: |
March 20, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B60C 23/0455 20130101;
B60C 23/0408 20130101; B60C 23/0462 20130101; B60C 23/0437
20130101; B60C 23/0484 20130101 |
International
Class: |
B60C 23/04 20060101
B60C023/04 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 23, 2016 |
FR |
1658968 |
Claims
1. A self-adaptive method for assisting in the inflation of tires
of a vehicle, the vehicle being stationary in an immobilization
mode, the method comprising: continuously measuring at least a
pressure of each tire by way of a wheel unit associated with each
tire, transmitting signals on a state of the tires via a wireless
link between each wheel unit and a central unit, the central unit
continuously analyzing these signals and then transmitting
information in relation to the state of the tires to an information
module, a pressure variation above a predetermined threshold of a
tire associated with each wheel unit and detected by the wheel unit
giving rise to transmission of a signal to the central unit, these
signals being transmitted by each wheel unit through
frequency-shift keying between two first predetermined frequencies
defining, between them, a first frequency band, wherein, when the
vehicle is stationary in an immobilization mode, each wheel unit is
reprogrammed such that each wheel unit transmits, to the central
unit, a first frequency-shift keyed signal with the first frequency
band and a second frequency-shift keyed signal with a second
frequency band wider than the first band.
2. The method as claimed in claim 1, wherein the first frequency
band is around 30 kHz and the second frequency band is equal to or
greater than 50 kHz.
3. The method as claimed in claim 1, wherein, as soon as reception
of the modulated signal from a wheel unit takes effect at the
central unit, this modulated signal being the first frequency-shift
keyed signal with the first frequency band or the second
frequency-shift keyed signal with the second frequency band, the
central unit is reprogrammed so as to perform filtering of the
received modulated signal using at least one of two different
filter bandwidths that alternate periodically.
4. The method as claimed in claim 3, wherein a period of
alternation between the two different bandwidths depends on a
duration of the signal, such that the received modulated signal is
able to be filtered with the two bandwidths if a first filtering
operation with one of the two bandwidths has not given a useful
signal.
5. The method as claimed in claim 3, wherein the two filter widths
are respectively a narrow width of around 50 kHz and a wide width
of around 300 kHz.
6. The method as claimed claim 3, wherein, upon reception of the
modulated signal from a wheel unit, the central unit, which is then
in a standby state, is reprogrammed so as to change to periodic
awake mode.
7. The method as claimed in claim 1, wherein a stoppage in the
immobilization mode is defined by an immobilization of the vehicle
for a duration greater than a predetermined threshold duration.
8. The method as claimed in claim 1, wherein each wheel unit and
the central unit are set by default to a driving mode detected by a
movement of the vehicle, for which driving mode each wheel unit is
programmed so as to transmit, to the central unit, a
frequency-shift keyed signal with the first frequency band and,
when the central unit has been reprogrammed so as to perform
filtering of the received modulated signal using at least one of
two different filter bandwidths, the central unit is programmed so
as to perform filtering of the modulated signal using the larger of
the filter bandwidths, each wheel unit also being programmed, in
this driving mode, so as to transmit the frequency-shift keyed
signals with the first frequency band.
9. The method as claimed in claim 8, wherein the signals that are
frequency-shift keyed by each wheel unit are transmitted, when the
vehicle is stationary in the immobilization mode, at a second bit
rate lower than a first bit rate which is that of the driving
mode.
10. A system for assisting in the inflation of tires of a vehicle,
the vehicle being stationary in an immobilization mode, the system
comprising: a wheel unit continuously measuring at least the
pressure of each tire, a central unit, a wireless link transmitting
signals on the state of the tires between each wheel unit and the
central unit, the central unit continuously analyzing these signals
and transmitting information in relation to the state of the tires
to an information module, a pressure variation above a
predetermined threshold of a tire associated with each wheel unit
and detected by a detector of the wheel unit giving rise to the
transmission of a signal to the central unit by a transmitter of
the wheel unit, these signals being transmitted by each wheel unit
through frequency-shift keying between two first predetermined
frequencies defining, between them, a first frequency band,
wherein, when the vehicle is stationary in an immobilization mode,
the system implements the method as claimed in claim 1 and
comprises means for reprogramming each wheel unit such that each
wheel unit transmits, to the central unit, a first frequency-shift
keyed signal with the first frequency band and a second
frequency-shift keyed signal with a second frequency band wider
than the first band.
11. The method as claimed in claim 2, wherein, as soon as reception
of the modulated signal from a wheel unit takes effect at the
central unit, this modulated signal being the first frequency-shift
keyed signal with the first frequency band or the second
frequency-shift keyed signal with the second frequency band, the
central unit is reprogrammed so as to perform filtering of the
received modulated signal using at least one of two different
filter bandwidths that alternate periodically.
12. The method as claimed in claim 4, wherein the two filter widths
are respectively a narrow width of around 50 kHz and a wide width
of around 300 kHz.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is the U.S. National Phase Application of
PCT International Application No. PCT/FR2017/052488, filed Sep. 18,
2017, which claims priority to French Patent Application No.
1658968, filed Sep. 23, 2016, the contents of such applications
being incorporated by reference herein.
FIELD OF THE INVENTION
[0002] The invention relates to a self-adaptive method for
assisting in the inflation of tires of a vehicle, the vehicle being
stationary in what is called an immobilization mode, the method
consisting in continuously measuring at least the pressure of each
tire by way of a wheel unit, and in transmitting signals on the
state of the tires via a wireless link between each wheel unit and
a central unit. The central unit continuously analyzes these
signals and then transmits information in relation to the state of
the tires to an information module.
[0003] A pressure variation above a predetermined threshold of a
tire associated with each wheel unit, detected by the wheel unit,
gives rise to the transmission of a signal to the central unit,
these signals being transmitted by each wheel unit by
frequency-shift keying between two first predetermined frequencies
defining, between them, a first frequency band.
[0004] In a primary application, the invention relates to systems
installed on motor vehicles for monitoring and managing tire
pressure, called TPMS ("tire pressure monitoring system")
systems.
BACKGROUND OF THE INVENTION
[0005] As monitoring the pressure of tires is essential to the
safety of motor vehicles, pressure-monitoring systems, such as TPMS
systems, were created to perform this function and installed on
motor vehicles.
[0006] These primarily comprise sensors that measure the pressure
of the tires and transfer it to the central unit. This central unit
collects and analyzes the tire pressure data via wireless links.
The result of these analyses is generally displayed on the
dashboard of the vehicle. Such a system is therefore able to inform
the driver of the tire pressure in real time, or just produce a
visual or audio announcement if pressure anomalies are detected by
this system. It is also possible for the driver to receive this
information on a mobile telephone.
[0007] This may be performed by way of frequency-shift keyed
signals. Frequency-shift keying is known under the acronym FSK. In
the following text, frequency-shift keying will be used to denote
this type of digital frequency modulation, which is performed
between predetermined frequencies.
[0008] One example of a wheel unit communicating with a central
unit through frequency-shift keying in order to measure a pressure
or the temperature inside a tire is given for example by document
US 2015/377741, incorporated herein by reference.
[0009] As mentioned above, a method for assisting in the inflation
of tires of a vehicle is performed when the vehicle is stationary,
this being given the name in immobilization mode. In these cases of
the vehicle being stationary, a major problem of a risk of poor
transmission between the tires and the central unit arises.
[0010] Specifically, when the wireless links between the pressure
sensors of the wheel units and the central unit encounter
obstacles, the level of reception of the signals at the central
unit decreases to the point that these signals may become
inaudible. The positions of the wheels that generate these
reception problems are called black spots.
[0011] If the stoppage of the vehicle corresponds, for one or more
wheels, to black spot conditions, the transmission remains impacted
throughout the entire duration of the stoppage, as the position of
the wheel does not vary. These black spots may be caused for
example by the position of the transmitter antenna of a wheel unit,
by reflection on the ground of part or of all of the transmitted
signal, or by the relative position of the wheel unit with respect
to the central unit.
[0012] Experience has shown that, in a stationary position, the
probability of the wheel unit of at least one wheel being in a
black spot position is significant and non-negligible. When a wheel
unit is stationary at a black spot, the budget of its link to the
central unit is greatly degraded, up to around -90 dBm. In this
case, the signal received by the central unit is no longer able to
be analyzed due to the excessively low signal-to-noise ratio.
[0013] No prior art document has taken into account this problem of
stopping on a black spot for frequency-shift keyed signals. Common
practice is to search, for frequency-shift keying, for a
predetermined frequency band that is as narrow as possible. This
was supposed to optimize frequency-shift keying communication and
guarantee it in all conditions, which is clearly not the case for a
black spot.
[0014] Document FR 3 002 492, incorporated herein by reference,
describes a self-adaptive method for assisting in the inflation of
tires of a vehicle, consisting in continuously measuring at least
the pressure of each tire by way of a wheel unit, and in
transmitting signals on the state of the tires via a wireless link
between each wheel unit and a central unit at least two different
bit rates, called high bit rate and low bit rate. The central unit
then continuously analyzes these signals and then transmits
information in relation to the state of the tires to an information
module. A continuous measurement of the shift/immobility state of
the vehicle is also provided to the central unit and to the wheel
unit.
[0015] Although decreasing the bit rate proves to be effective,
given that replacing a high-bit rate transmission with a low-bit
rate transmission allows an improved signal-to-noise ratio and
enables a reception sensitivity gain, thus allowing the signals to
be received, this document does not give any indication with regard
to modifying parameters of signal frequency-shift keying that could
solve the problem of defective transmission due to the presence of
a black spot for at least one of the wheels of a stationary motor
vehicle.
SUMMARY OF THE INVENTION
[0016] The problem underlying the present invention is that of
improving defective transmission between a wheel unit of a
stationary vehicle and a central unit due primarily to a fixed
position of the wheel that is not favorable to transmission between
its wheel unit and the central unit, in the context of a method for
assisting in the inflation of tires of a vehicle.
[0017] To this end, an aspect of the present invention relates to a
self-adaptive method for assisting in the inflation of tires of a
vehicle, the vehicle being stationary in an immobilization mode,
the method consisting in continuously measuring at least the
pressure of each tire by way of a wheel unit, in transmitting
signals on the state of the tires via a wireless link between each
wheel unit and a central unit, the central unit continuously
analyzing these signals and then transmitting information in
relation to the state of the tires to an information module, a
pressure variation above a predetermined threshold of a tire
associated with each wheel unit and detected by the wheel unit
giving rise to the transmission of a signal to the central unit,
these signals being transmitted by each wheel unit through
frequency-shift keying between two first predetermined frequencies
defining, between them, a first frequency band, characterized in
that, when the vehicle is stationary in immobilization mode, each
wheel unit is reprogrammed such that each wheel unit transmits, to
the central unit, a first frequency-shift keyed signal with the
first frequency band and a second frequency-shift keyed signal with
a second frequency band wider than the first band.
[0018] The prior art provided for a frequency-shift keyed signal to
restrict the frequency band for as long as possible in order to
optimize communication between a wheel unit and the central unit
and guarantee this communication in all conditions. There was
therefore a prejudice in the prior art to operate with a wide
frequency band.
[0019] An aspect of the present invention overcomes this prejudice
by operating with two modulated signals each having a different
bandwidth. An aspect of the present invention applies in the
specific case of a black spot, which is caused by a position of the
sensor in the wheel that is unfavorable to good transmission. This
unfavorable position persists, given that the wheel is not turning,
as the vehicle is stationary.
[0020] Therefore, an aspect of the present invention is not to seek
to optimize communication between the wheel unit in question and
the central unit for all positions of the wheel, but to allow
transmission for a fixed wheel position involving a black spot when
the vehicle is stationary. As soon as the vehicle is in driving
mode with a turning wheel, there is no longer a need to use two
modulated signals each with a different frequency bandwidth, and
the system changes back to a mode with a single modulated signal
with a narrow frequency bandwidth, as advocated by the prior
art.
[0021] According to the prior art, those skilled in the art sought
to transmit the signal without considering the position of the
areas of no transmission. A protocol with a pseudorandom time
interval makes it possible to cover the constraint of no
transmission linked to an area of no transmission. Over time, this
protocol makes it possible to cover the entire wheel, and thus
guarantee that the signal has been transmitted correctly. This
approach is not possible if the vehicle is immobilized, that is to
say in parking mode, the area of no transmission being invoked, the
pseudorandom protocol being ineffective because the vehicle is
immobile. This is solved by the an aspect of present invention,
which guarantees transmission even in parking mode.
[0022] The reprogramming of each wheel unit such that each wheel
unit transmits, to the central unit, first and second modulated
signals is performed automatically, without external assistance,
upon detection of conditions representative of the immobilization
mode of the vehicle.
[0023] Advantageously, the first frequency band is around 30 kHz
and the second frequency band is equal to or greater than 50
kHz.
[0024] Advantageously, as soon as reception of the modulated signal
from a wheel unit takes effect at the central unit, this modulated
signal being the first frequency-shift keyed signal with the first
frequency band or the second frequency-shift keyed signal with the
second frequency band, the central unit is reprogrammed so as to
perform filtering of the received modulated signal using at least
one of two different filter bandwidths that alternate
periodically.
[0025] The central unit receives two modulated signals having
different frequency bands. Each of these modulated signals is to be
filtered by way of filtering having a specific bandwidth. As the
central unit is not able to recognize whether the modulated signal
that it receives is modulated by the first frequency band or by the
second frequency band, the central unit applies to it the two
filtering operations with different bandwidths.
[0026] Advantageously, the period of alternation between the two
different bandwidths depends on a duration of the signal, such that
the received modulated signal is able to be filtered with the two
bandwidths if a first filtering operation with one of the two
bandwidths has not given a useful signal. This makes it possible to
apply the two filtering operations with different bandwidths to the
first or to the second modulated signal so as to optimize filtering
of the signals.
[0027] Advantageously, the two filter widths are respectively a
narrow width of around 50 kHz and a wide width of around 300
kHz.
[0028] Advantageously, upon reception of the modulated signal from
a wheel unit, the central unit, which is then in standby state, is
reprogrammed so as to change to periodic awake mode. Automatically
putting the central unit into standby when the vehicle is
stationary allows energy to be saved as soon as the vehicle is
stationary, this stoppage being able to be a stoppage in order to
inflate the tires and not requiring the central unit to remain
awake. By contrast, in the specific case of inflating the tires,
the central unit should be awake.
[0029] Advantageously, the stoppage in immobilization mode is
defined by an immobilization of the vehicle for a duration greater
than a predetermined threshold duration. This duration makes it
possible to check that the vehicle is stationary for a certain
time, for example for a maintenance operation or due to the driver
leaving the vehicle, and that the vehicle is therefore not likely
to be restarted straight away.
[0030] Advantageously, each wheel unit and the central unit are set
by default to a driving mode detected by a movement of the vehicle,
for which driving mode each wheel unit is programmed so as to
transmit, to the central unit, a frequency-shift keyed signal with
the first frequency band and, when the central unit has been
reprogrammed so as to perform filtering of the received modulated
signal using at least one of two different filter bandwidths, the
central unit is programmed so as to perform filtering of the
modulated signal using the larger of the filter bandwidths, each
wheel unit also being programmed, in this driving mode, so as to
transmit the frequency-shift keyed signals with the first frequency
band.
[0031] In driving mode, the modulated signal has a narrow frequency
band, and the central unit performs specific filtering at this
narrow frequency band. Each wheel unit therefore returns to the
normal transmission conditions and the central unit therefore
returns to the normal reception conditions defined by default by a
nominal driving mode.
[0032] Advantageously, the signals that are frequency-shift keyed
by each wheel unit are transmitted, when the vehicle is stationary
in immobilization mode, at a second bit rate lower than a first bit
rate which is that of the driving mode.
[0033] In this optional feature of the method according to an
aspect of the invention, the modulated signals are transmitted,
when the vehicle is stationary in immobilization mode, at a bit
rate low enough that the reception sensitivity of the central unit
makes it possible to avoid virtually any reception interference.
Thus, in the event of reception subjected to interference by a
black spot, the signal level received by the central unit may for
example drop below -90 dBm or lower.
[0034] Replacing a high-bit rate transmission of the modulated
signals with a low-bit rate transmission allows an improved
signal-to-noise ratio and enables a reception sensitivity gain. For
example, a high bit rate value, or first bit rate in driving mode,
in this measurement field may be 9.6 Kbits/s, and a lower bit rate
or low bit rate value, as advocated by an aspect of the present
invention, may be 2 Kbits/s. This thus allows the reception of
modulated signals that could previously have been lost at a high
bit rate.
[0035] An aspect of the invention also relates to a system for
assisting in the inflation of tires of a vehicle, the vehicle being
stationary in an immobilization mode, the method consisting in
continuously measuring at least the pressure of each tire by way of
a wheel unit, in transmitting signals on the state of the tires via
a wireless link between each wheel unit and a central unit, the
central unit having means for continuously analyzing these signals
and then means for transmitting information in relation to the
state of the tires to an information module, a pressure variation
above a predetermined threshold of a tire associated with each
wheel unit and detected by detection means of the wheel unit giving
rise to the transmission of a signal to the central unit by
transmission means of the wheel unit, these signals being
transmitted by each wheel unit through frequency-shift keying
between two first predetermined frequencies defining, between them,
a first frequency band, characterized in that, when the vehicle is
stationary in immobilization mode, the system implements such a
method and comprises means for reprogramming each wheel unit such
that each wheel unit transmits, to the central unit, a first
frequency-shift keyed signal with the first frequency band and a
second frequency-shift keyed signal with a second frequency band
wider than the first band.
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] Other features, aims and advantages of aspects of the
present invention will become apparent upon reading the following
detailed description and with reference to the appended drawings,
given by way of nonlimiting example and in which:
[0037] FIG. 1 is a schematic depiction of one embodiment of a tire
management system of a vehicle able to implement the method
according to an aspect of the invention;
[0038] FIG. 2 shows an evolution of the sensitivity of a receiver,
which is the central unit, as a function of a shift that
corresponds to the frequency bandwidth of a frequency-shift keyed
signal;
[0039] FIG. 3 shows a flow chart of the steps of one exemplary
implementation of the method according to an aspect of the
invention on the side of a wheel unit,
[0040] FIG. 4 shows a flow chart of the steps of one preferred
exemplary implementation of the method according to an aspect of
the invention on the side of the central unit.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0041] With reference to the basic diagram of FIG. 1, the four
tires 1a to 1d of a motor vehicle, not shown, are each equipped
with a wheel unit 3a to 3d. These wheel units 3a to 3d include
antennas 4a to 4d that transmit signals, transmitted via
radiofrequency links 5a to 5d, to a central unit 2. The four tires
1a to 1d also each include a movement sensor 6a to 6d.
[0042] Each of these sensors 6a to 6d periodically transmits, by
way of a wireless link, not shown, the stationary or movement
information from the respective wheel unit 3a to 3d to the central
unit 2. A central movement sensor 7 is electrically connected to
the central unit 2. It is dedicated to the information from the
central unit 2 on the stationary or moving situation of the
vehicle, and communicates its own measurement thereto.
[0043] The central unit 2 thus has the complete status of the
movement/immobilization of the vehicle from all of the movement
sensors 7, 6a to 6d. The central unit 2 is intended to continuously
analyze the information provided by the wheel units 3a to 3d and by
the movement sensors 7, 6a to 6d: for example pressure,
temperature, acceleration and "moving or stationary" state in the
example illustrated.
[0044] The central unit 2 includes at least the following elements:
a microcontroller 2a, a receiver 2b and an antenna 2c. This central
unit 2 thus receives the signals coming from the wheel units 3a to
3d with respective powers that will vary depending on the position
of the antennas 4a to 4d and on the surroundings of the wheel units
3a to 3d and on the central unit 2. For example, the engine and the
devices of the vehicle may influence the surroundings of the wheel
units 3a to 3d and interfere with the signals, in particular
through reflections on the ground.
[0045] These power variations may lead to low levels of reception
by the central unit 2. After analyzing the received information,
the central unit 2 displays, on a display module 9, the relevant
information for the driver, in particular: immediate warning in the
event of a severe pressure reduction for at least one tire and, for
minor pressure reductions, for example less than 0.10 bar, warning
communicated only when the vehicle is next stationary. This may
also be performed on the screen of a mobile telephone equipped with
the appropriate application.
[0046] The signals from each wheel unit 3a to 3d to the central
unit 2 are radiofrequency frequency-shift keyed signals between two
predetermined frequencies. According to the prior art, this is
performed both in a driving mode while the vehicle is driving and
in an immobilization mode while the vehicle is stationary, for
example at a service station in order to inflate its tires.
[0047] In the latter case, it has been established that, as the
wheel is immobile, if the stoppage of the vehicle corresponds, for
one or more wheels, to black spot conditions, the transmission
remains impacted throughout the entire duration of the stoppage. To
overcome this drawback, an aspect of the present invention proposes
to differentiate the immobilization mode from the driving mode for
the transmission of modulated signals from each wheel unit 3a to 3d
to a central unit 2 by sending, in immobilization mode, two
modulated signals containing the same information but differing in
terms of their bandwidth between two predetermined frequencies,
which will be described in further detail in the following
text.
[0048] FIG. 3 describes in more detail an exemplary flow chart of
the steps of one embodiment of the method according to an aspect of
the invention at a wheel unit 3a to 3d for achieving the
sensitivity improvement at the central unit 2, as described above.
This flow chart comprises the following steps.
[0049] After the start or beginning 29 of this method, a test,
called start of stoppage test 30, on the moving/stationary state of
the vehicle is performed by way of a continuous measurement
provided by a movement sensor of a wheel unit 3a to 3d. If the
result of the start of stoppage test 30 indicates a driving state
of the vehicle, this being represented by N for No at the output of
this start of stoppage test 30, the wheel unit 3a to 3d is set to a
driving mode, which is its nominal state, this being referenced at
41.
[0050] Digitized periodic signals are then transmitted in this
mode, this being referenced at 42. The method then returns to the
start 29. These digitized periodic signals are frequency-shift
keyed signals between two first predetermined frequencies defining,
between them, a first frequency band, which will be the narrower
frequency band of the two frequency bands for transmitting two
types of modulated signal during an immobilization mode in the
context of an aspect of the present invention, which mode will be
described in more detail further on.
[0051] If the result of the start of stoppage test 30 indicates a
stationary state of the vehicle, this being represented by Y for
Yes at the output of this start of stoppage test 30, a pressure
variation start test 32 is performed on the pressure variation
.DELTA.P of the tire of the wheel unit 3a to 3d with respect to a
given threshold value, for example equal to 0.1 bar, so as to
detect inflation of the tire, for example in a service station.
[0052] If the pressure variation start test 32 is positive, this
being represented by Y for Yes at the output of this pressure
variation test 32, the wheel unit concludes, in step 33, that
inflation is detected, for example when the vehicle is present at a
service station in order to inflate the tire associated with the
wheel unit 3a to 3d. After step 33 of detecting inflation has
concluded, a time countdown is initialized in step 34, in
particular but without limitation starting from a duration of 120
seconds in this example.
[0053] A time countdown test 36 relates to the countdown of step 34
counting down to zero. Thus, for as long as the elapsed duration
remains less than the reference value, 120 seconds in the example,
this being referenced by the output No N at this time countdown
test 36, the wheel unit 3a to 3d then switches its setting to
immobilization mode, this being referenced at step 37.
[0054] During this immobilization mode 37, each wheel unit 3a to 3d
is reprogrammed such that each wheel unit 3a to 3d transmits, to
the central unit 2, a first frequency-shift keyed signal with the
first frequency band and a second frequency-shift keyed signal with
a second frequency band wider than the first frequency band. This
reprogramming step, which is essential in the context of an aspect
of the invention, is referenced at step 43.
[0055] This reprogramming may also simplify the signals, so as to
make them shorter by making them contain only the identification of
the wheel unit 3a to 3d and therefore of the tire associated with
pressure information, this being referenced 38.
[0056] Optionally, the signals that are frequency-shift keyed by
each wheel unit 3a to 3d are transmitted, when the vehicle is
stationary in immobilization mode, at a second bit rate lower than
the first bit rate, the second bit rate being low enough that a
reception sensitivity of the central unit 2 makes it possible to
avoid virtually any reception interference. This is applicable for
the frequency-shift keyed signals between both the narrow first
frequency band and the wider second frequency band.
[0057] Optionally, the wheel unit 3a to 3d may also transmit frames
at a high bit rate so as to redundantly secure the transmission.
The low-bit rate signals are shorter in terms of bit number, so as
to have a temporal duration at most equal to those of the high-bit
rate signals in "driving" mode, so that the duration of the low-bit
rate signals also complies with official standardization standards.
To this end, these signals contain a limited amount of information,
containing only its identity and the pressure value in the example.
The advantage of using this low bit rate is that of improving the
link budget in the event of stoppage on a black spot.
[0058] The immobilization mode 37 continues as long as the method
runs through a loop including the following steps. A first step of
this loop relates to an end of stoppage test 44 for the vehicle,
which is substantially equivalent to the start of stoppage test but
at the end of stoppage.
[0059] If the response to this end of stoppage test 44 is No N,
this corresponding to the detection of a vehicle that is no longer
immobilized, there is a change to driving mode 41, this
representing the first possibility of exiting the loop of the
immobilization mode. In the event of a response No N to the end of
stoppage test 44, the method, by switching the wheel unit 3a to 3d
to driving mode 41, follows the steps 42, 29 described above
starting from this step in driving mode 41.
[0060] If the response to this end of stoppage test 44 is Yes Y,
this corresponding to the detection of a vehicle that is still
immobilized, the loop is continued by a pressure variation end test
referenced 46.
[0061] In this pressure variation end test 46, if the pressure
variation of the tire of the wheel unit 3a to 3d in question is
lower than the given threshold value, this value advantageously
being the same threshold value as for the pressure variation start
test 32, this being illustrated by the output No N of this test,
there is a return to the time countdown test 36. If the countdown
has not yet reached zero, this being illustrated by the output No N
of the time countdown test 36, the immobilization mode 37 is
maintained for the wheel unit 3a to 3d. This corresponds for
example to a stationary situation, in an inflation station at the
end of the process of inflating a tire or tires.
[0062] Starting from the time at which the reference duration of
the time countdown test 36 is reached, this being illustrated by
the output Yes Y of this time countdown test 36, it is concluded
that the inflation process has ended, and there is a return to the
start 29 of the method, this representing the second possibility of
exiting the loop of the immobilization mode.
[0063] Another possibility of exiting this loop of the
immobilization mode is the detection, in the pressure variation end
test 46, of a pressure variation in the tire of the wheel unit 3a
to 3d greater than or equal to the predetermined threshold value,
which is advantageously the same as for the pressure variation
start test 32. In the event of a response Yes, symbolized by Y, to
this test 46, it is concluded that inflation is detected 33,
therefore that the vehicle is present at a service station for
inflating the tire corresponding to the wheel unit 3a to 3d. The
method then follows steps 34, 36, 37, 38, 44, 46 described above
starting from step 33, with the wheel unit 3a to 3d being kept in
its specific reprogramming for the immobilization mode or the wheel
unit 3a to 3d being changed to its driving mode at 41, 42.
[0064] The wheel units 3a to 3d of the vehicle, generally 4 of
them, each follow the method illustrated in this FIG. 3. These
wheel units 3a to 3d do not necessarily switch from "driving" mode
to "immobilization" mode at the same time, for example due to not
simultaneously receiving pressure variations.
[0065] Without limitation, for frequency-shift keyed signals
between two frequencies, the first frequency band for the first
signals is around 30 kHz and the second frequency band for the
second signals is equal to or greater than 50 kHz.
[0066] FIG. 2 shows an evolution of the sensitivity sens of a
receiver, which is the central unit 2, as a function of a shift dev
that corresponds to the frequency bandwidth of a frequency-shift
keyed signal. A variation of 3 dBm between a shift or frequency
bandwidth of +/-30 kHz, which may be the first narrower bandwidth,
and a shift of +/-50 kHz, which may be the second wider bandwidth,
is observed.
[0067] The operation of the central unit 2, which will be
illustrated in FIG. 4, may make it possible to receive both
frequency-shift keyed signals between a narrow frequency band,
coming from at least one wheel unit 3a to 3d in driving mode,
previously referenced 41 in FIG. 3, on the one hand, and pairs of
frequency-shift keyed signals respectively between a narrow
frequency band and a wide frequency band coming from at least one
wheel unit in immobilization mode, previously referenced 37 in FIG.
3, on the other hand.
[0068] As illustrated in FIG. 4, the self-adaptive method for
assisting in the inflation of tires of a vehicle on the side of the
central unit 2, which is optional in the context of an aspect of
the present invention, comprises a start of stoppage test step 50
similar to the stoppage test 30 performed at the wheel unit 3a to
3d and shown in FIG. 3. It is then determined whether the vehicle
is moving or stationary.
[0069] If the vehicle is moving, this corresponding to the response
No N, the central unit 2 receives, in step 57, signals in "driving"
mode, that is to say frequency-shift keyed signals between two
first predetermined frequencies defining, between them, a first
frequency band, which may be the narrower band of the two types of
signal transmitted by each wheel unit 3a to 3d in immobilization
mode.
[0070] If the vehicle is stationary, this corresponding to the
response Yes Y, a time countdown test 51 similar to the time
countdown test 36 performed at the wheel unit 3a to 3d illustrated
in FIG. 3 is performed, although this one may have a different
reference duration. This reference duration may be equal to 45
seconds in the example, whereas the reference duration for the
wheel unit 3a to 3d may be 120 seconds.
[0071] As long as the elapsed duration remains less than 45
seconds, this corresponding to the response No N to the time
countdown test 51, a pressure variation detection test 52 is
performed so as to determine whether a tire is currently being
inflated. If the pressure variation detected in the pressure
variation detection test 52 remains lower than a predetermined
threshold, for example 0.1 bar, this corresponding to the response
No N to the test, the central unit 2 is receiving in driving mode
without reprogramming for the reception of the modulated signals,
this driving mode being referenced 57.
[0072] By contrast, if the pressure variation detected in the
pressure variation detection test 52 becomes greater than the
predetermined threshold, this corresponding to the output Yes Y of
FIG. 4, the central unit 2 concludes that the vehicle has stopped
at a station for inflating tires of the vehicle and switches to
immobilization mode 53 so as to receive two signals, coming from a
wheel unit 3a to 3d, which are frequency-shift modulated
respectively between two first predetermined frequencies defining,
between them, a first frequency band and a second frequency band.
For the central unit 2, the immobilization mode 53 influences the
filtering of these two signals, this being illustrated in step
54.
[0073] In immobilization mode with detection of a pressure
variation, as soon as reception of the modulated signal from a
wheel unit 3a to 3d takes effect at the central unit 2, this
modulated signal may be the first frequency-shift keyed signal with
the first frequency band or the second frequency-shift keyed signal
with the second frequency band.
[0074] As shown in step 55, the central unit 2 is then reprogrammed
so as to perform filtering of the received modulated signal using
at least one of two different filter bandwidths that alternate
periodically. Specifically, it is unknown whether the central unit
2 will receive a modulated signal of the first type with a first
frequency band or a modulated signal of the second type with a
second frequency band.
[0075] The first filter bandwidth is suitable for filtering
modulated signals with a first frequency band and the second filter
bandwidth is suitable for filtering modulated signals with a second
frequency band.
[0076] The two filter widths are respectively a narrow width of
around 50 kHz and a wide width of around 300 kHz. In immobilization
mode, upon reception of the first modulated signal from a wheel
unit 3a to 3d arriving at the central unit 2, the central unit 2,
which is then in standby state, is reprogrammed so as to change to
periodic awake mode.
[0077] There may be alternation between the two different
bandwidths. The period of alternation between the two different
bandwidths is adapted to a duration of the signal, such that the
received modulated signal is able to be filtered with the two
bandwidths if a first filtering operation with the first of the two
bandwidths has not given a useful signal. In parallel with this,
the central unit 2 may retain programming in driving mode for other
applications.
[0078] When the measured duration exceeds the reference duration,
for example 45 seconds, established in the duration countdown test
51, this corresponding to the output Yes Y of the duration
countdown test, the central unit 2 concludes that inflation of the
vehicle has stopped and switches to reception driving mode 59 in
order to receive the signals and filter them with just one
filtering band.
[0079] Step 54 illustrates the reception step after filtering of
the signals in driving mode 59 and in immobilization mode 53,
respectively after or before the reference duration of the time
countdown test 51 has been exceeded.
[0080] In driving mode 57 or 59, the central unit 2 receives only
modulated signals that always have one and the same frequency band.
These modulated signals are filtered with one and the same filter
bandwidth by the central unit 2.
[0081] In immobilization mode 53, optionally, if the wheel unit 3a
to 3d transmits information other than that in relation to the
pressure of its tire, the central unit 2 may also be configured in
"driving" mode so as to receive the signals in relation to this
information.
[0082] An aspect of the invention also relates to a system for
assisting in the inflation of tires of a vehicle, the vehicle being
stationary in an immobilization mode, the method consisting in
continuously measuring at least the pressure of each tire 1a to 1d
by way of a wheel unit 3a to 3d, and in transmitting signals on the
state of the tires 1a to 1d via a wireless link 5a to 5d between
each wheel unit 3a to 3d and a central unit 2. The central unit 2
has means for continuously analyzing these signals and then means
for transmitting information in relation to the state of the tires
1a to 1d to an information module 9, which may be a mobile
telephone.
[0083] A pressure variation above a predetermined threshold of a
tire associated with each wheel unit 3a to 3d and detected by
detection means of the wheel unit 3a to 3d gives rise to the
transmission of a signal to the central unit 2 by transmission
means of the wheel unit 3a to 3d, these signals being transmitted
by each wheel unit 3a to 3d by frequency-shift keying between two
first predetermined frequencies defining, between them, a first
frequency band.
[0084] According to an aspect of the invention, when the vehicle is
stationary in immobilization mode, the system implements a method
such as described above and comprises means for reprogramming each
wheel unit 3a to 3d such that each wheel unit 3a to 3d transmits,
to the central unit 2, a first frequency-shift keyed signal with
the first frequency band and a second frequency-shift keyed signal
with a second frequency band wider than the first band.
[0085] These reprogramming means may be integrated into each wheel
unit 3a to 3d or be present in the central unit 2, and
reprogramming signals may be sent to each wheel unit 3a to 3d.
[0086] Aspects of the invention are not limited to the exemplary
embodiments that are described and shown. Thus, various low bit
rate values may be chosen for the various cases of "immobilization"
mode that are found in this method: stationary situation with tire
inflation or simple parking situation.
[0087] This method could be integrated into a more complete method
incorporating all of the aspects of existing systems regarding
technical tire management. By way of example, a method that adjusts
the time at which the driver is informed depending on the
importance, or lack thereof, of the loss of pressure of a tire.
Moreover, the technique of repeatedly sending each information
frame ("time diversity") may also be added to the method according
to an aspect of the invention.
* * * * *