Note: Descriptions are shown in the official language in which they were submitted.
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DESCRIPTION
The present invention relates in general to systems
for communicating between a plurality of sensors and a
central unit, and in particular to systems of this type
which can be fitted, for example, on board articulated
vehicles.
Systems of the above speci1ed type are known in the
art, for example, from the GB patent application no.
G~-A-2 188 459 or from Italian Patent IT-B-l 219 753.
These systems can be used advantageously to transmit to a
central unit disposed in the driving cab of the motor
vehicle messages emitted by sensors associated with the
motor vehicle's wheels and lndicative of the fact that the
pressure of one or more of the tyres is insufficient or
excessive.
These systems are essentially constituted by a
central unit and a plurality of sensors installed for
example on the vehicle wheels. In operation of the system
these sensors are in communication relationship, for
example by means of radio waves, wlth the central unit. In
this way a central unit can receive messages transmltted
by the sensors, process them and present corresponding
information to the vehicle drlver.
For correct operation of the system it is necessary
that the central unit be in possession of informatlon
relating to the configuration of the system, in particular
as far as the sensors are concerned. Usually, in fact, the
central unit identifies the sen~ors by codes which these
latter associate wlth messages transmitted to the central
unit ltself. Naturally, this latter must be prelimlnary
cognizant of the codes allocated to the various sensors.
~oreover, in the event, for example, that one of the
sensors is broken or that its battery is discharged, the
central unit (which is cognizant of the existence of this
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sensor), upon not receivin~ any message from the sensor,
informs the driver of the occurrence o~ an anomaly so that
he can rectify it.
The lnstallation of systems of the above-described
type is partlcularly advantageous on board lndustrial
vehicles such as motor trucks, etc. These vehicles are
often composed of two separate vehicles, a tractor and a
trailer (or semi-trailer, for example a pivoted semi-
trailer). Typically, a given tractor does not necessarily
have a single specified trailer or semi-trailer associated
with it. It can happen rather that the same tractor may
have several different trailers or semi-trailers coupled
to it at different times, and in some cases the tractor
will travel without a trailer.
This practice, which is becoming ever more prevalent,
can create significant difficulties if it should be
desired to instal one of the above-mentioned systems on
board. In fact, each time that the tractor is coupled to a
dlfferent trailer it i5 neces~ary, for correct utilisatlon
of the system, to arrange that the central unit mounted on
the tractor, can have available all the information
relating to the new trailer, or may be informed of the
fact that the tractor will be travelling without a trail-
er. In prior art such systems it is possible to subject
the central unit to learning cycles for the purpose of
making it acquire informatlon concerning the configuration
of the system. However, the problem of obtalning this
result in a very short time remains open since thls
operation must be absolutely free of errors in order to
permit correct operation of the system. It is evident
that, in the case of frequent replacement of trallers, the
operation of reconfiguring the central unit (and the
system as a whole) becomes critical.
The ob~ect of the present invention is therefore that
of permitting variations in the configuration stored in
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the central unit to be made in a rapid and safe manner,
thereby permitting, for example, frequent replacement of
the trallers whilst simultaneously maintaining the ser-
viceability of the parameter detecting system lnstalled on
board the tractor.
According to the present invention this object is
achieved by a system having the characteristics set out in
the appended claims.
In summary, in one of the possible embodiments
thereof, the invention provides for the memorisation of
configuration data relating to a given vehicle (for
example a trailer) in memory means of permanent or semi
permanent type, for example a read only memory (ROM) or an
erasable programmable read only memory (EEPROM) and by
configuring these memory means as a separate additional
unit which can be selectively associated with the central
unit. This additional unit was therefore be formed as a
small module, card or electronic key, which can be linked
to the central unit, for example placed on the dashboard
of the principal vehicle (for example the tractor), with a
simple coupling operation. A socket can be provided on the
central unit for this purpose, which can receive and
temporarily, but stable, lock the electronic key and which
allows an easy connection and disconnection of this key by
an electronic connector which upon connection o~ the key
connects the key's memory to the circuits of the central
unit via the electronic key's own connector. The reconfig-
uration of the central unit is, in practice, achieved by
the simple operation of the introducing the key. This
procedure is very advantageous since each traller can be
provided with its own speciflc configuration key intended
to constitute an element of the trailer equipment (being,
for example, retained when not ln use, ln the envelope
contalning the trailer's traffic documents). When the
trailer is linked to the tractor the key can thus be
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simply inserted into the central unit of the tractor
thereby immediately effecting the reconfiguration of the
~ystem. Upon uncoupling of the trailer from the tractor it
will be sufficlent to remove the key from the central unit
installed on the tractor to indicate to this central unit
that, for the moment, the tractor is not connected to any
trailer.
A further advantageous characteristic of the present
inventions is as follows.
A key associated with the central unit will be able
to be programmed by this latter if it is necessary to
record the configuration information relating to a new
trailer, or whenever it is necessary to vary the previous-
ly stored configuration information (for example to change
a sensor). In this way the central unit can conveniently
act as an interface for storing the configuration data in
the trailer keys.
One embodiment of the present invention will be
described herelnbelow, purely by way of example, with
reference to the attached figures of the drawings, in
whlch:
Figure 1 ls a schematic representation of a parameter
detection system operating according to the present
invention as installed on two separate vehicles;
Figure 2 is a functional block schematic representa-
tion of the detection system operating according to the
present invention; and
Figure 3 is a perspective schematic representation of
the central unit and of the conflguration key of the
system.
A system of the type according to the present inven-
tion comprises, with reference to figures 1 and 2, a
central unit 1 mounted on board a first vehlcle A, for
example in the cabin of a tractor of an articulated truck.
Unit 1 in turn includes a processor module 4, a display
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device 5, a data setting/control device 6 (for example a
keyboard), a communica~ion device 7 for communication by
radio waves, and an antenna 8. The system further includes
an assembly of sensors each constituted by a processor and
transmission module 10a mounted on a respective wheel lla
of the vehicle A and carrying associated therewith one or
more respective sensors 12a for detection of parameters
such as, for example, the inflation pressure and/or
temperature of the tyres on the respective wheelsj and an
associated memory (for example of the EEPROM type). Each
module 10a is, therefore, able to process the signal from
the sensor 12a and communicate via radio with the central
unit 1 by means of a radio frequency device and an associ-
ated antenna 13a. In a substantially similar configura-
tion, on another vehicle B, typically a semi-trailer
intended to be coupled to the tractor A, there is provided
a second assembly of sensors comprising processor an
transmission modules 10b with associated respectlve
sensors 12b mounted on the wheels llb of the trailer B and
also capable of communicating with the central unit by
means of a respectlve radio frequency device and antenna
13b. In particular, the processor module 4 is provided
with an electronic memory (usually this is also an EEPROM)
which contalns the data relatinq to the sensors lOa, 12a
on the vehicle A, such as, for example, the sensor codes
and the normal pressures of the wheels associated with the
sensors.
All the above is widely known per se in the art: see
in this connection, for example, the two patents already
clted in the introductlon to the present descrlption.
If it is desired to link the vehicle A (tractor) with
the vèhlcle B (trailer or semi-trailer - chosen ln general
from an assortment of different trailers intended to be
connected to one or more tractors in dependence of the
requirements of use) the problem arises of putting the
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central unit on into a condition such that it detects that
the vehicle B has been linked to the vehicle A and that it
is desired for the central unit 1 also to manage the
parameter detection sensors 10b, 12b installed on the
vehicle B. To this end the system accordlng to the inven-
tion includes a key 2 in which there is a memory 9.
By complementary connectors 3 provided on the central
unit 1 and on the key 2 (figure 3) the key 2 itself can be
connected both mechanically and electrically to the
central unit 1. In this way, by connecting the key 2 into
the unit 1 the electronic memory 9 of the key 2 can be put
into connection with the module 4 so as to make available
thereto the data contained in the memory 9. In the cur-
rently preferred embodiment the memory is an EEPROM, for
example of the 93C06 type, with a capacity of 256 bytes.
In particular, the memory 9 contains, in the form of
an addressable and updatable table, the configuration data
relatlng to the sensors 10b, 12b of the vehicle B such as
the ldentificatlon codes and/or the nominal pressures of
the tyres to which the sensors are associated on the
vehicle B. Simply by insertion of the key 2 the module 4
is able immediately to have available (by the connection
to the memory 9) the system configuration data necessary
for management of the sensors 12b. The operation for
connecting of key 2 to the central unit 1 is extremely
simple; making reference to Figure 3 it is in fact suffi-
cient simply to insert the key 2 into a complementary
socket 14 provided on the central unit 1. By this opera-
tion connection between the respective connectors 3 on the
key 2 and the central unit 1 will be effected, thereby
completing the operation. The three following tables
reproduce, with reference to a currently preferred embodl-
ment, the organlsation of the memories relatlng to the
sensors (table 1), the central unit (table 2) and the
sensors of the second group (table 3).
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TABLE 1 - EEPROM MEMORY FOR SENSORS
BYTE-OH Code )
E~YTE-OL Code ) Expressed in hexadecimal
BYTE-lH Code )
BYTE-lL Number of sensors between 0 and 15 hexadecimalYTE-2H Value of the pressure variation in tenths of a
BAR so that updating of the central unit is
lndicated.YTE-2L Value of the temperature variation in 0.5C so
that updating of the central unit is indicatedYTE-3H Number of steps of the ADC correspondlng to
the value of the pressure of 0 BAR (position-
ing of the curve of the electronic pressure
sensor).YTE-3L Number of steps of the ADC corresponding to
the value of the pressure from 6.4 BAR (second
positioning point).YTE-4H Number of steps of the ADC correspondlng to
the temperature value of -27C (positionlng of
the curve of the electronic temperature
sensor).YTE-4L Number of steps of the ADC corresponding to
the temperature value 4C (second positloning
point).YTE-5H Must contain a fixed number (for example 25)
ln hexadecimal.YTE-5L Repetition time of the "sensor operativen
message expressed in 102 units of wake up time
(example with wake up of 2.5 seconds of number
inserted will be the multiplier of about ~5
minutes).YTE-6H Sensor supply time before reading with ADC.
Units of about 180 mlcrosec.YTE-6~ Transmltter supply time expressed in units of
about 200 microsec.
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8YTE-7H Unit of delay tlme in the repetition of the
alarm transmission linked to the number of the
sensor. Expressed in units of about 320
millisec.
BYTE-7L Wait tlme for response from the central unit
expressed in units of about 80 millisec.
~YTE-8H Number of attempts to transmit alarm signal to
the central unit if immediate response not
obtained therefrom.
BYTE-8L Number of attempts to transmit to the central
unit the updating values read if immediate
response not obtained therefrom.
BYTE-9H Number of attempts to transmit the "sensor
operative" message to the central unit if
immediate response not obtained therefrom.
BYTE-9L Delay time to repeat the transmission to be
added to the variable delay as a function of
the wheel number (BYTE-7H). Expressed in units
of about 320 millisec.
BYTE-AH Percentage departure from the nominal pressure
to indlcate the high pressure alarm. Expressed
ln steps of 3.125%.
BYTE-AL Percentage departure from the nominal pressure
value to indicate the low pressure alarm.
Expressed in steps of 3.125%.
BYTE-BH Range used ln the micro processor.
BYTE-BL High temperature alarm threshold. Value
expressed in units of 0.5C.
BYTE-CH Value of the pressure at which the tyre must
be considered as totally deflated ~after
achievement of this condition self learning of
the value of the nominal working pressure can
be obtained. Value expressed in tenths of a
~AR.
BYTE-CL Not used.
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YTE-DH Value to be multiplled by the value contained
in the next half byte to obtain the receiver
supply time expressed ln units of about 250
microsec.YTE-DL See description of preceding half byte.YTE-EH Pressure value check time to consider the tyre
deflated expressed in units of about 2.5 sec.YTE-EL Pressure value check time to consider the tyre
inflated. Expressed in units of about 2.5 sec.YTE-FH Flag used by the micro processor for self
learning.YTE-FL Value of the nominal working pressure to which
reference is made for determination of the
alarm threshold. If self learning is not
utilised necessary to set its value upon
production.
TABLE 2 - EEPROM MEMORY FOR CENTRAL UNITYTE-OH Central unit code, recorded in production.YTE-OL Central unit code, recorded durlng production.YTE-lH Central unlt c
ode, recorded durlng productlon.YTE-lL Number of sensors intended to be in first
group. Must be programmed upon installation,
but to be able to test the central unit it is
necessary during production to set in a value
different from 0.YTE-2H Central unlt transmitter supply time. Value
expressed in unlts of about 250 microsecs.YTE-2L Number of strings of codes which it is desired
to transmit from the central unit.YTE-3H Sensor silence time after which the central
unit will conslder the sensor broken. Ex-
. pressed in units of about 4.5 minutes.YTE-3L Insert a fixed value (eg 45)
TABLE 3_- EEPROM FOR 2ND GROUPYTE-OH Code of second group sensors to be memorised
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during production.YTE-OL Code~of second group of sensors, to be memo-
rised during production.YTE-lH Code of second group of sensors, to be memo-
rlsed during productlon.YTE-lL Number of sensors lntended to be in second
group. This number is programmed upon instal-
lation.
The information on the configuration of the sensors
lOb-12b of the trailer B will have been loaded on the
memory 9 upon installation of sensors lOb, 12b, by means
of a suitable teaching unit. The key 2 therefore consti-
tutes an item of equipment intended to accompany the
trailer B to be inserted in the central unit 1 of the
various tractors A to which the trailer B will be subse-
quently coupled.
This information can also be modified by rewriting or
replacing the memory 9 whenever the sensors lOb, 12b on
the trailer B are reconfigured or modified (replacement of
damaged sen~or~, addition of new sensors, etc).
In particular, the arrangement accordlng to the
ingnetion lends itself to being utilised as a learning
and/or modification unit for the memory 9 associated with
a certain trailer B whatever the central unlt 1.
It will be sufficient to engage the key 2 with this
memory 9 in a central unlt 1 to perform the learning cycle
of the key 2 in question by wrlting the configuration data
relatlng to the sensors lOb of trailer into the memory 9.
This result can be obtained, for example and ln another
way, by an operator who loads the said data by acting on
the keyboard 6 of the central unit 1.
At this polnt the key 2 is ready for use and can be
separated from the unit 1 used for programming it.
The system configuration described lends itself
further to the following mode of operation. Each of the
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sensors is arranged so that it can be disactivated for a
certain time lnterval (eg 20 seconds). This is achieved by
command from the central unit 1 or by separating the
associated sensor 12a 12b from a tyre which is inflated to
a given pressure chosen as the reference pressure. The
sensor then acts in an automatic manner to read and store
(usually within itself) the value of thls reference
pressure as soon as it is reactivated (for example as soon
as the associated sensor 12a 12b is connected back onto
the tyre).
This result is usually obtained by the processor
means (for example a microprocessor) present in the
modules lOa, lOb. At this point each sensor is able to
transmit this pressure value (and possibly a corresponding
temperature value) to the central unit 1. This latter will
be able to identify these values as coming from a given
sensor in dependence on the system configuratlon data.
This also relates to the traller B the configuration data
of which are stored in the key 2.
At the same tlme each sensor lOa 12a lOb 12b is able
to utilise the stored reference pressure level in order ~o
signal possible anomalous variations of the tyre pressure.
This mode of operation lends itself in particular to
those situatlons of use in which the tyre inflation
pressure of the vehicle must be adapted to difference
operating and/or load conditions: for example when the
vehicle changes from a fully loaded to an unloaded state
or when it is intended to change from an asphalt road onto
excavated land. In each case it is thus possible to
arrange that the sensors automatically learn the pressure
value to be considered as a reference value.
Finally, each detection device composed of a sensor
12a, 12b and associated communication means lOa lOb and
13a 13b, intended to be installed upon the wheels lla llb
of the tractor A or the trailer B can be provided wlth an
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electrlcal connector 14a 14b complementary to an assoclat-
ed electrical connector 15 pro~lded on the central unit 1.
By puttlng the central unit 1 (with its associated key 2
in the case of the sensors lOb, 12b of the traller B) in
programme mode lt is sufflcient temporarlly to connect the
sald detection devlces ln succession by means of these
complementary electrlcal connectors 14a 14b and 15 to the
central unit 1 to personalise the detectlon device by
memorising within it the code identifying the tractor A or
the trailer B, and associated wlth this - the code identi-
fying the wheel to which the detection device is linked.
This function in particular allows the use of sensors lOa,
12a; lOb, 12b which are all substantially identical to one
another with the possibility of "personalising" them in
dependence on the specific installations.
The embodiment of the present invention described
here has characteristics which are purely exemplary and
non limitative of the scope of the present invention. To a
man skllled in the art, in fact, it will be evident that
the present inventlon can be produced in different forms
and applied to different environments from that described.
For example, the present lnvention could be utilised to
detect other groups of different parameters from tyre
pressure of the vehlcle wheels (for example temperature,
fluid levels, electrical parameters etc.). Specifically,
one can conslder monitoring vehicle tyre temperature based
on a discrete relationship between pressure and tempera-
ture (eg as given by Boyle and Charles from standard
physical laws).
As for communicatlon, it could also take place not by
means of radio waves but, for example, by means of elec-
trical cables, optical fibres or magnetic coupling, etc.
In particular, the reference, made several times in the
present description, to the possible use on industrial
units (tractor plus trailer) must not be interpreted as in
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any sense limitative in that the invention lends itself to
being utilised, ,for example, on motor cars or other
vehicles such as trucks, buses or special vehicles such as
non-road vehicles and/or vehicles which use fluids such as
water to pressurize the tyres. In this case, the sensors
considered in the foregoing function with said fluids.
Agaln in respect of the sensors it is worthwhile
recelling, as examples of sensors which can be used
advantageously within the framework of the present inven-
tion, those disclosed in Italian Patent 1, 189, 631 or US
Patents 4, 69~, 273 and 4, 804, 808.
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