U.S. patent application number 10/082419 was filed with the patent office on 2003-08-28 for restraint system interface arrangement for a seat belt tension sensor.
Invention is credited to Constable, Robert K., Gray, Charles A., Patterson, James F., Sullivan, Stuart S..
Application Number | 20030160509 10/082419 |
Document ID | / |
Family ID | 27660361 |
Filed Date | 2003-08-28 |
United States Patent
Application |
20030160509 |
Kind Code |
A1 |
Patterson, James F. ; et
al. |
August 28, 2003 |
RESTRAINT SYSTEM INTERFACE ARRANGEMENT FOR A SEAT BELT TENSION
SENSOR
Abstract
An improved vehicle restraint system includes a seat belt
tension sensor and an occupant detection control module for
characterizing the occupant of a vehicle seat to determine whether
to allow or suppress deployment of supplemental inflatable
restraints for the occupant. The belt tension sensor includes
on-board signal processing circuitry and is coupled to occupant
detection control module via a two wire interface that both powers
the sensor and its signal processing circuitry and supports
communication of belt tension data to the occupant detection
control module. The sensor produces an electrical signal responsive
to seat belt tension, and the processing circuitry generates one of
a specified number of messages pertaining to the range of the
measured tension, and then modulates the current through the two
wire interface to communicate the generated message to the occupant
detection control module.
Inventors: |
Patterson, James F.;
(Greentown, IN) ; Gray, Charles A.; (Noblesville,
IN) ; Constable, Robert K.; (Kokomo, IN) ;
Sullivan, Stuart S.; (Peru, IN) |
Correspondence
Address: |
ROBERT M. SIGLER
DELPHI TECHNOLOGIES, INC
Legal Staff Mail Code: CT10C
P.O. Box 9005
Kokomo
IN
46904-9005
US
|
Family ID: |
27660361 |
Appl. No.: |
10/082419 |
Filed: |
February 26, 2002 |
Current U.S.
Class: |
307/10.1 |
Current CPC
Class: |
B60R 21/01522 20141001;
B60R 21/0155 20141001; B60R 21/01546 20141001 |
Class at
Publication: |
307/10.1 |
International
Class: |
B60R 021/01 |
Claims
1. A restraint system for the occupant of a vehicle seat, including
a sensor for measuring tension in a seat belt associated with said
seat, and an occupant detection module for determining whether to
allow or suppress deployment of restraints for the occupant based
on measured parameters including the measured seat belt tension,
the system further comprising: first and second conductors for
supplying a system voltage from the occupant detection module to
said sensor; sensor circuitry disposed with the sensor for
characterizing an output signal of the sensor relative to the
determination of whether to allow or suppress deployment, and for
transmitting a corresponding message to said occupant detection
module by modulating a current through a circuit path including
said first and second conductors; and detection circuitry within
the occupant detection module for detecting the current modulation
to decode the message and the corresponding characterization of the
sensor output signal for purposes of determining whether to allow
or suppress deployment of the restraints.
2. The restraint system of claim 1, wherein: the sensor circuitry
includes a voltage regulator coupled to the first and second
conductors for developing an operating voltage for said sensor and
said sensor circuitry which is lower than said system voltage so
that such operating voltage is not affected by the modulation of
the current through said first and second conductors.
3. The restraint system of claim 1, wherein the sensor circuitry
characterizes the sensor output signal such that the messages
transmitted to the occupant detection module indicate a
predetermined tension range within which the measured tension
lies.
4. The restraint system of claim 1, wherein the sensor circuitry
characterizes the sensor output signal such that the messages
transmitted to the occupant detection module indicate a failure of
said sensor when the sensor output signal is outside a
predetermined range of values.
5. The restraint system of claim 1, wherein the sensor circuitry
comprises: processing circuitry for characterizing the sensor
output signal and developing the corresponding message; and
modulating circuitry coupled between said first and second
conductors, and activated by said processing circuitry to transmit
the developed message.
Description
TECHNICAL FIELD
[0001] This invention relates to a motor vehicle inflatable
restraint system including a seat belt tension sensor for
characterizing the occupant of a vehicle seat to determine whether
to allow or suppress deployment of restraints for the occupant, and
more particularly to a system arrangement for processing and
communicating information provided by the seat belt tension
sensor.
BACKGROUND OF THE INVENTION
[0002] Various occupant-responsive sensing devices can be employed
to characterize the occupant of a vehicle seat for purposes of
determining whether deployment of air bags and other restraints
should be allowed or suppressed. For example, it is generally
desired to allow normal deployment for an adult, to reduce
deployment force for a child, and to suppress deployment entirely
for an infant seat secured to the vehicle seat with a seat belt. A
particularly effective and yet inexpensive way of achieving this
functionality is to sense both the seat belt tension and the
occupant weight applied to the bottom cushion of the seat. In
general, the measured occupant weight may be reduced in proportion
to the measured seat belt tension to be more reflective of the
actual occupant weight applied to the seat, and seat belt tension
in excess of a calibrated value is indicative of a cinched down
infant seat.
SUMMARY OF THE INVENTION
[0003] The present invention is directed to an improved and cost
effective mechanization of a vehicle restraint system including a
seat belt tension sensor and an occupant detection module for
characterizing the occupant of a vehicle seat to determine whether
to allow or suppress deployment of supplemental inflatable
restraints for the occupant. According to the invention, the belt
tension sensor includes on-board signal processing circuitry and is
coupled to occupant detection module via a two wire interface that
both powers the sensor and its signal processing circuitry and
supports communication of belt tension data to the occupant
detection module. The sensor produces an electrical signal
responsive to seat belt tension, and the processing circuitry
generates one of a specified number of messages pertaining to the
range of the measured tension, and then modulates a loop current in
the two wire interface to communicate the generated message to the
occupant detection module.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIG. 1 is a system diagram of a vehicle restraint system,
including a belt tension sensor and an occupant detection module
according to this invention.
[0005] FIG. 2 is a partial cross-sectional view of the belt tension
sensor of FIG. 1
[0006] FIG. 3 is a circuit diagram illustrating pertinent circuitry
of the belt tension sensor and occupant detection module of FIG.
1.
[0007] FIG. 4 is a timing diagram illustrating a communication
protocol for sending messages from the belt tension sensor to the
occupant detection module.
[0008] FIGS. 5 and 6 depict flow diagrams representative of
software routines executed by the occupant detection module of FIG.
1 according to this invention.
[0009] FIG. 7 depicts a flow diagram representative of a software
routine executed by the belt tension sensor circuit of FIG. 3
according to this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0010] The present invention is disclosed in the context of a
vehicle restraint system 10 including an airbag control module
(ACM) 12, driver frontal and side air bags 14, 16, and passenger
frontal and side airbags 18, 20. The ACM 12 determines whether and
when to deploy the various airbags 14, 16, 18, 20 based on
acceleration data obtained from a frontal crash sensor 22, a driver
side crash sensor 24, a passenger side crash sensor 26, and
occupant status information obtained from occupant detection module
(ODM) 28. In general, the occupant status information may indicate
simply whether to allow or suppress deployment, but in certain
applications may provide additional occupant detail that enables
ACM 12 to suitably control the deployment force of the respective
air bags. The ODM 28 is responsive to the output Ws of a seat
sensor 34 indicative of the occupant weight applied to a vehicle
seat, a seat belt buckle switch 36 that indicates if a seat belt
for the vehicle seat is buckled or unbuckled, and a belt tension
sensor (BTS) 38 that indicates the amount of tension or force
applied to the seat belt. As indicated in FIG. 1, the seat sensor
34 in the illustrated mechanization is a pressure sensor responsive
to the fluid pressure in a seat cushion bladder 32, although other
information such as the temperature of the cushion or bladder is
usually required to obtain reliable occupant weight data over a
wide range of ambient conditions; see for example, the U.S. Pat.
Nos. 5,987,370, 6,101,436, 6,138,067 and 6,246,936, which are
assigned to the assignee of the present invention and incorporated
herein by reference.
[0011] The BTS 38 may take various forms, as set forth, for
example, in the Research Disclosure No. 41402, October, 1998, Page
1304, incorporated herein by reference. However, FIG. 2 illustrates
a particularly advantageous mechanization in which BTS 38 is
fastened to the vehicle floor outboard of the seat, and the seat
belt 50 passes through a sensor slot 48. The slot 48 is formed in
the main body of the sensor case 40, and the case 40 further
includes a tang 42 with an opening 44 for fastening BTS 38 to the
vehicle floor. When the seat belt 50 is in use, it engages an
armature 46 supported within the case 40, and tension in the seat
belt 50 biases armature 46 rightward as viewed in FIG. 2 against
the bias force of springs 52 and 54. The rest position of armature
46 is defined by the stop 56, and rightward displacement of
armature 46 is measured by a Hall Effect sensor 62 positioned
between a magnet 58 affixed to the armature 46 and a magnet 60
affixed to the case 40. The sensor 62 produces an Output signal
that is indicative of magnetic field strength, and such signal is
applied to a circuit board 66 via conductor 64. The circuit board
66 supports circuitry as described below in reference to FIG. 3 for
processing the sensor output signal and communicating a belt
tension message to ODM 28 via a conductor pair sheathed in the
cable 68.
[0012] FIG. 3 depicts the circuits of BTS 38 and ODM 28 in block
diagram format. The two wire interface comprising the conductors 70
and 72 is used both for supplying power from ODM 28 to BTS 38 and
for communicating belt tension messages from BTS 38 to ODM 28.
Within ODM 28, the conductor 70 is coupled to the vehicle ignition
voltage Vign (typically 12 VDC) through a current limiting resistor
74 and a switch 76 that opens or closes in response to the signal
on control line 78. The control line 78 is selectively activated by
a microprocessor-based ECU 80, which also activates a transistor 82
via resistor 84 whenever the control line 78 is activated to close
the switch 76. Within BTS 38, the sensor output signal on line 64
is applied as an input to the analog-to-digital converter (ADC)
input port of a microprocessor-based ECU 86, and the conductor 70
is supplied as an input to a voltage regulator (VR) 88 that
supplies a regulated output voltage VDD (such as 5 VDC) to Hall
Effect Sensor 62 and ECU 86 via line 90. A ground or reference
voltage is supplied from ODM 28 to BTS 38 via conductor 72, the
transistor 82 and the resistors 92 and 94. Thus, operating power is
supplied to BTS 38 from ODM 28 when ECU 80 activates the control
line 78.
[0013] As more fully described below in reference to FIG. 7, the
ECU 86 creates a digital representation of the sensor output
signal, and determines a corresponding belt tension range. In the
illustrated embodiment, for example, there are eleven legitimate
belt tension ranges (0-3 lbs., 3-6 lbs., 6-9 lbs., 9-12 lbs., 12-15
lbs., 15-18 lbs., 18-21 lbs., 21-24 lbs., 24-27 lbs., 27-30 lbs.,
and over-30 lbs.), a failed low range (ERRlow) and a failed high
range (ERRhigh). A message indicative of the determined belt
tension range is then communicated to ODM 28 by modulating the
conduction of a transistor 96 via resistor 98 in accordance with
the timing diagram of FIG. 4. Each modulation pattern has a fixed
period such as 100 msec, with a different number of pulses and/or
pulse-widths occurring within the period. For example, a series of
five two-msec pulses is used to represent the belt tension range of
12-15 lbs. The emitter of transistor 96 is coupled to the conductor
72, while the collector of transistor 96 is coupled to conductor 70
via the parallel connected resistor 100 and capacitor 102. When the
transistor 96 is modulated to a conductive state, the voltage on
conductor 70 falls to a value determined by the resistors 74, 100,
92 and 94 (which is still higher than the VDD output of voltage
regulator 88), and the loop current in conductors 70 and 72
increases to a higher-than-normal value. This change in the loop
current is detected by the comparator 104 in ODM 28, which compares
the voltage across resistor 94 to a threshold Vthr to produce a
digital output signal on line 106 that is supplied as an input to
the ECU 80.
[0014] As described below, the ECU 80 decodes the belt tension
message transmitted by BTS 38, and uses the corresponding belt
tension range to determine if airbag deployment should be allowed
or suppressed. If the belt tension range is indicative of a cinched
infant seat (i.e., above a calibrated value such as 30 lbs.), the
occupant status is set to SUPPRESS to suppress airbag deployment.
Otherwise the belt tension range is used to compensate the measured
seat weight Ws, or to inform ACM 12 of a failure of BTS 38.
[0015] The flow diagrams of FIGS. 5-6 represent software routines
executed by the ECU 80 of ODM 28 according to this invention. The
routine of FIG. 5 is continuously executed during vehicle operation
to update the suppression status based on the various inputs
depicted in FIG. 1, and to send the suppression status to ACM 12,
whereas the routine of FIG. 6 is an interrupt service routine
executed in response to a logic level transition on the comparator
output line 106 for receiving and decoding the belt tension message
sent by BTS 38.
[0016] Referring to FIG. 5, the block 110 is initially executed to
initialize system variables including the suppression status. Then
the blocks 112 and 114 are executed to read various input signals
such as the measured seat weight Ws and the seat belt buckle switch
state, and to read the current belt tension range. The diagnostics
block 116 determines if the input signals are consistent and within
normal ranges, and the block 118 then determines the suppression
status based on the measured seat weight, the seat belt buckle
state and the seat belt tension range. For example, the belt
tension range can be used to detect the presence of a cinched down
infant seat, or to compensate the measured seat weight Ws so that
it more accurately represents occupant weight. If an infant seat is
detected, the suppression status is set to SUPPRESS; otherwise the
suppression status is set to either SUPPRESS or ALLOW depending on
the magnitude of the adjusted seat weight and the seat belt buckle
switch state. The block 120 then sends the suppression status to
ACM 12, and possibly also to a driver display (not shown). As
indicated at block 122, the blocks 112-120 are repeatedly executed
during vehicle operation, and when the vehicle ignition switch is
turned off, the block 114 performs shutdown tasks to complete the
routine.
[0017] As indicated above, the interrupt service routine of FIG. 6
is executed in response to a logic level transition on the
comparator output line 106. The blocks 126 and 128 determine the
pulse time and level, and the block 130 sets a timer to measure the
duration of the next pulse. This process is repeated at each
interrupt until block 132 determines that the message pulse train
is complete. At Such point, the block 134 is executed to decode the
belt tension message based on the number of pulses and their
duration.
[0018] The flow diagram of FIG. 7 represents a software routine
executed during vehicle operation by the ECU 86 of BTS 38 for
processing the Output signal of Hall Effect sensor 62, and sending
a corresponding belt tension range message to ODM 28. The block 136
is initially executed to initialize system variables including the
belt tension range. Then the blocks 138 and 140 are executed to
read and filter the digital version of the Hall Effect output
signal, and the block 142 determines if the signal is within a
normal range of values. If the diagnostics indicate that the signal
is above the normal range, the blocks 144 and 146 set the belt
tension range signal (SIGNAL) to HIGH FAULT; if the signal is below
the normal range, the blocks 148 and 150 set SIGNAL to LOW FAULT.
Otherwise, the block 152 sets SIGNAL to a value corresponding to
the measured belt tension, either by table look-up or successive
comparison of the filtered signal to a series of calibrated
thresholds. Then the block 154 is executed to send the determined
SIGNAL to ODM 28 by modulating the conduction of a transistor 96 as
described above in reference to the block diagram of FIG. 3 and the
timing diagram of FIG. 4. As indicated at block 156, the blocks
138-154 are repeatedly executed during vehicle operation, and when
the vehicle ignition switch is turned off, the block 158 performs
shutdown tasks to complete the routine.
[0019] In summary, the present invention provides a cost effective
arrangement for interfacing a remote belt tension sensor to an
occupant detection module in a vehicle restraint system. The two
wire interface not only supplies power to from the occupant
detection module to the sensor and its associated signal processing
circuitry, but also supports communication of belt tension messages
to the occupant detection module through modulation of the loop
current in the two wire interlace. Functions customarily performed
in the occupant detection module, such as signal processing and
diagnostics, are instead performed by the sensor circuitry, and the
belt tension data is transferred to the occupant detection module
in a digital format to reduce susceptibility to error from spurious
electromagnetic interference.
[0020] While this invention has been described in reference to the
illustrated embodiment, it will of course be recognized that
various modifications in addition to those mentioned above will
occur to those skilled in the art. For example, the message
protocol of FIG. 4 may be modified to include more or fewer ranges,
the belt tension sensor 38 may be different than shown, and so on.
Accordingly, it should be understood that restraint systems
incorporating these and other modifications may fall within the
scope of this invention, which is defined by the appended
claims.
* * * * *