United States Patent [19J
`Fu
`
`111111
`
`1111111111111111111111111111111111111111111111111111111111111
`US005848661A
`[11] Patent Number:
`[45] Date of Patent:
`
`5,848,661
`Dec. 15, 1998
`
`[54]
`
`VEHICLE SEAT ASSEMBLY INCLUDING AT
`LEAST ONE OCCUPANT SENSING SYSTEM
`AND METHOD OF MAKING SAME
`
`[75]
`
`Inventor: David T. Fu, Rochester Hills, Mich.
`
`[73]
`
`Assignee: Lear Corporation, Southfield, Mich.
`
`[21]
`
`Appl. No.: 735,326
`
`[22]
`
`Filed:
`
`Oct. 22, 1996
`
`[51]
`[52]
`[58]
`
`[56]
`
`Int. Cl.6
`..................................................... B60K 28/00
`U.S. Cl. ........................... 180/273; 280/735; 297/410
`Field of Search ............................. 280!735; 297/410,
`297/391; 318/568.1, 567; 180/273
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`3,420,572
`4,082,354
`4,645,233
`4,807,934
`4,834,420
`4,935,680
`5,071,160
`5,074,583
`5,095,257
`5,118,134
`5,366,241
`5,398,185
`5,400,487
`
`1!1969 Bisland ................................... 297/410
`4/1978 Renner eta!. .......................... 297/410
`2/1987 Bruse et a!. .
`2/1989 Sakakibara .............................. 297/403
`5/1989 Sankrithi et a!. .
`6/1990 Sugiyama ................................ 318/567
`12/1991 White et a!. .
`12/1991 Fujita et a!. .
`3/1992 Ikeda et a!. .......................... 318/568.1
`6/1992 Mattes et a!. .
`11/1994 Kithil .
`3/1995 Omura .
`3/1995 Gioutsos et a!. .
`
`5/1995 Steffens, Jr., eta!. .
`5,413,378
`5,474,327 12/1995 Schousek .
`Primary Examiner-Christopher P. Ellis
`Attorney, Agent, or Firm-Brooks & Kushman P.C.
`ABSTRACT
`
`[57]
`
`A vehicle seat assembly comprising occupant sensing sys(cid:173)
`tems for use in headrest adjusting and/or air bag actuation
`systems. One sensing system includes a passive transducer
`array in the form of pressure transducers such as force
`sensing resistors vertically spaced in a first embodiment in
`a headrest cushion of the vehicle seat. In a second
`embodiment, the pressure transducers are vertically spaced
`in a backrest cushion of the seat. The pressure transducers
`generate signals which are processed by a controller to
`generate a control signal to control a bidirectional headrest
`motor coupled to the headrest of the vehicle seat. In another
`sensing system, occupant sensors in the form of either force
`sensing resistors or mechanical switches are embedded in
`the seat back cushion and the seat bottom cushion to
`generate signals which are processed by the controller to
`generate a control signal for use by an air bag actuation
`circuit to prevent air bag deployment when the controller
`determines that the vehicle seat is either unoccupied or is
`occupied by a rear-facing child car seat. The controller
`includes control logic to distinguish between a properly
`seated occupant and the rear-facing infant seat based on the
`electrical output signals from the occupant sensors located in
`the seat back and bottom cushion.
`
`13 Claims, 6 Drawing Sheets
`
`20 22
`
`~10
`
`24
`
`48
`
`CONTROLLER
`
`AIR BAG ACTUATION CIRCUIT
`
`IPR2016-00292 - Ex. 1003
`Toyota Motor Corp., Petitioner
`
`1
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`U.S. Patent
`
`Dec. 15, 1998
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`5,848,661
`
`1
`VEHICLE SEAT ASSEMBLY INCLUDING AT
`LEAST ONE OCCUPANT SENSING SYSTEM
`AND METHOD OF MAKING SAME
`
`TECHNICAL FIELD
`
`This invention relates to vehicle seat assemblies and
`method of making same and, in particular, to vehicle seat
`assemblies including at least one occupant sensing system
`and methods of making same.
`
`BACKGROUND ART
`
`Vehicle seat assemblies come in a wide variety of shapes
`and sizes. Many vehicle seat assemblies currently include
`integrated front seat belts. Such assemblies eliminate the
`need to anchor the shoulder belts to a pillar between the front
`and rear windows, instead containing the entire belt appa(cid:173)
`ratus within the seat. Some advantages of such integrated
`seat belts is that they eliminate unsightly shoulder belts
`hooked to the pillars and also improves entry and exit in
`some vehicles. The integrated belts also make it easier to
`remove the second and third rows of seats in minivans.
`Furthermore, such integrated seat belts are generally more
`comfortable because the belts move with the seat.
`Vehicle seat assemblies including occupant sensing sys(cid:173)
`tems are well known. One method for the automatic adjust(cid:173)
`ment of headrest height involves active transducers (i.e.
`ultrasound or infrared light-emitter transmitter and receiver
`pairs). The transmitters emit non-visible waves and receiv-
`ers at various locations sense the reflected or interrupted 30
`signal from the head of the occupant.
`For example, the Bruse et al. U.S. Pat. No. 4,645,233
`discloses an adjustment mechanism for automatically
`adjusting the height of a headrest of vehicle seat wherein a
`sensor detects the seating height of a person seated on the 35
`vehicle seat in a normal position and controls a motor for the
`height adjustment of the headrest in accordance with detec(cid:173)
`tion results. In one embodiment, one light emitter-receiver is
`located in the upper area of the front side of a headrest, while
`another light emitter-receiver detects the height of a shoul- 40
`der of the person.
`Another vehicle seat assembly including an occupant
`sensing system is disclosed in the Bauer U.S. Pat. No.
`5,431,447. Sensors generate signals which are processed by
`a microcomputer and to, in turn, generate a control signal
`which actuates a motor in a seat belt restraint system. The
`sensors sense characteristics of an occupant such as weight
`and location of the occupant in the vehicle.
`Other vehicle seat assemblies include occupant sensing
`systems in order to generate a control signal which can be
`used by an air bag actuation circuit to inhibit air bag
`deployment. When one or more air bags are provided in an
`automobile, the air bag may be stored in many different
`locations such as in a steering wheel, in a seat bolster, a door 55
`panel or in an instrument panel of the vehicle.
`Such systems are desirable and are often times preferred
`over occupant sensing systems mounted in front of the
`vehicle occupant. Mounting an occupant position sensor in
`front of a vehicle occupant or to the side of the occupant may
`provide a false reading because of an object placed between
`the position sensor and the occupant. For example, the
`object may be the hand of the vehicle occupant, the crossed
`legs of the occupant, or a map or the like held between the
`position sensor and the occupant.
`The Steffens, Jr. et al. U.S. Pat. No. 5,439,249 discloses
`a vehicle seat assembly including an occupant sensing
`
`2
`system having a sensor mounted in the seat back. Preferably,
`the sensor is an ultrasonic sensor having a sound beam.
`The Mattes et al. U.S. Pat. No. 5,118,134 discloses a
`vehicle seat assembly including an occupant sensing system
`5 having a position sensor in the headrest of the vehicle seat.
`The position sensor has at least one light transmitter and one
`light receiver.
`The Fujita et al. U.S. Pat. No. 5,074,583 discloses a
`vehicle seat assembly including an occupant sensing system
`10 including a plurality of pressure sensors having a spaced
`relationship relative to one another to detect pressure acting
`on the seat back and seat cushion. The sensors typically are
`electrostatic capacitance sensors to detect a pressure distri(cid:173)
`bution across the seat device in order to provide a control
`15 signal for an air bag system.
`The Schousek U.S. Pat. No. 5,474,327 discloses a vehicle
`seat assembly including an air bag restraint system wherein
`air bag deployment is inhibited when an occupied, rear-
`20 facing infant seat is present. The sensing apparatus com(cid:173)
`prises eight variable resistance pressure sensors located in a
`seat cushion.
`The Steffens, Jr. et al. U.S. Pat. No. 5,413,378 also
`discloses a vehicle seat assembly including an occupant
`25 sensing system having an occupant position sensor which
`takes the form of an ultrasonic sensor.
`U.S. Pat. Nos. 5,071,160; 5,232,243; 5,366,241; 5,398,
`185; and 5,400,487 all discloses passenger seat detecting
`and position determining sensors for controlling passive
`restraint systems including air bags in vehicles.
`U.S. Pat. No. 4,834,420 discloses an air bag-equipped
`child seat.
`
`SUMMARY OF THE INVENTION
`
`50
`
`An object of the present invention is to provide a vehicle
`seat assembly including an occupant sensing system and
`method of making same wherein strategically placed occu(cid:173)
`pant sensing sensors are incorporated in the seat to generate
`signals for use by a controller of the system which, in turn,
`generates a control signal for use by an occupant restraint
`system.
`Another object of the present invention is to provide a
`vehicle seat assembly including at least one occupant sens-
`45 ing system and method of making same wherein occupant
`sensing sensors are strategically placed in the vehicle seat to
`generate signals for use by a controller of the system which,
`in turn, generates a control signal for use to control a motor
`coupled to a headrest of the seat assembly to adjust the
`height of the headrest.
`Automatic headrest adjustment is to protect an occupant
`during a rear crash (whiplash). A properly adjusted headrest
`can reduce neck injury. Also, when the headrest carries a
`seatbelt, automatic adjustment of the headrest automatically
`adjusts the position of the seatbelt.
`Still further in carrying out the above objects and other
`objects of the present invention, a method is provided for
`manufacturing a vehicle seat assembly including a vehicle
`seat having a headrest and back and bottom cushions
`60 wherein a passive transducer array is positioned in the back
`cushion so as to sense height of an occupant in the seat.
`In carrying out the above objects and other objects of the
`present invention, a vehicle seat assembly constructed in
`accordance with the present invention is provided. The
`65 assembly includes a vehicle seat having seat back and
`bottom cushions to support corresponding back and bottom
`parts of an occupant seated on the vehicle seat and a headrest
`
`8
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`

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`5,848,661
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`4
`the passive transducer array to the controller, the motor to
`the headrest and the controller to the motor to obtain the
`assembly.
`Preferably, the passive transducer array includes three
`5 pressure transducers and the step of mounting includes the
`step of mounting the three pressure transducers in a
`vertically-spaced relationship in the back cushion of the
`headrest. In one embodiment, the back cushion is a headrest
`cushion. In another embodiment, the back cushion is a seat
`10 back cushion.
`The above objects and other objects, features, and advan(cid:173)
`tages of the present invention are readily apparent from the
`following detailed description of the best mode for carrying
`out the invention when taken in connection with the accom-
`15 panying drawings.
`
`3
`having a headrest cushion with a variable height relative to
`the bottom cushion. The assembly also includes an
`occupant-sensing system having a passive transducer array
`mounted in one of the seat back and headrest cushions to
`detect pressure caused by the occupant seated on the vehicle
`seat and to generate corresponding electrical output signals.
`Finally, the assembly includes a controller coupled to the
`passive transducer array for processing the electrical output
`signals and generating an electrical control signal adapted to
`automatically control a motor coupled to the headrest to
`adjust the variable height of the headrest cushion.
`In one embodiment, the passive transducer array is
`mounted in the headrest cushion to detect location of a head
`of the occupant seated on the vehicle seat relative to the
`headrest. The controller generates the control signal based
`on a seating height of the occupant seated on the vehicle
`seat.
`In another embodiment, the passive transducer array is
`mounted in the seat back cushion to detect location of an at
`least one acromion of the occupant seated on the vehicle seat
`relative to the seat back cushion. The controller generates
`the control signal based on a sitting acromial height of the
`occupant seated on the vehicle seat.
`Preferably, the passive transducer array includes three
`vertically spaced pressure transducers. Also, preferably, the
`pressure transducers are force-sensing resistors.
`The assembly also preferably includes a seat belt coupled
`to the headrest to move therewith. In this case, when the
`headrest is at the proper height (based on the height of a
`shoulder of the occupant), then the seatbelt is also at the
`proper height to optimize the protection of the occupant.
`Further in carrying out the above objects and other objects
`of the present invention, a vehicle seat assembly constructed
`in accordance with the present invention is provided. The 35
`assembly includes a vehicle seat having seat back and
`bottom cushions to support corresponding back and bottom
`parts of an occupant seated on the vehicle seat. The assembly
`also includes an occupant-sensing system including at least
`one occupant-sensing sensor mounted in the seat back 40
`cushion to generate a first electrical output signal and a
`second occupant-sensing sensor mounted in the bottom
`cushion to generate a second electrical output signal in
`response to pressure caused by the occupant seated on the
`vehicle seat. Finally, the assembly includes a controller 45
`coupled to the sensors for processing the electrical output
`signals and generating an electrical control signal. The
`controller includes control logic to distinguish between a
`properly seated occupant and a rear-facing infant seat on the
`vehicle seat based on the electrical output signals.
`Preferably, the control signal is adapted for use by an air
`bag activation system to prevent an air bag from being
`deployed in the absence of an occupant (or a rear-facing
`child seat) on the vehicle seat.
`Also, preferably, a pair of occupant-sensing sensors are 55
`mounted in the seat back cushion to generate the first
`electrical output signal.
`Still further in carrying out the above objects and other
`objects of the present invention, a method is provided for
`making a vehicle seat assembly. The method includes the 60
`step of providing a vehicle seat including a headrest and
`back and bottom cushions. The headrest has a variable
`height relative to the bottom cushion. The method also
`includes the steps of mounting a passive transducer array in
`the back cushion so as to sense height of an occupant in the 65
`seat, mounting a motor in the vehicle seat, and providing a
`controller. Finally, the method includes the steps of coupling
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`30
`
`FIG. 1 is a perspective view of a vehicle passenger side
`20 seat assembly including an occupant sensing system and
`automatic head restraint adjustment system constructed in
`accordance with the present invention;
`FIG. 2 is a side elevational view illustrating different
`positions in a vehicle seat for a passive transducer array and
`25 three different positions of a headrest of the seat;
`FIG. 3 is a side elevational view illustrating a rear-facing
`child car seat;
`FIG. 4 is a view similar to the view of FIG. 3 wherein the
`child car seat is forward facing;
`FIGS. Sa and Sb are computer-generated images illustrat(cid:173)
`ing the distribution of body pressure on car seat bottom and
`back cushions, respectively, for a first occupant;
`FIG. Sc is a schematic view of a vehicle seat assembly
`which has alphanumeric characters corresponding to the
`images of FIG. Sa, Sb, 6a and 6b;
`FIGS. 6a and 6b are images corresponding to the images
`of FIGS. Sa and Sb for a different height occupant of the
`vehicle seat;
`FIG. 7a is a side elevational schematic view of a vehicle
`seat having first and second occupant sensing sensors
`mounted therein; and
`FIG. 7b is a block diagram flow chart illustrating control
`logic for use in a controller to distinguish between a properly
`seated occupant and a rear-facing infant seat positioned on
`the vehicle seat.
`
`50
`
`BEST MODE FOR CARRYING OUT THE
`INVENTION
`
`Referring now to the drawing Figures, there is illustrated
`in FIG. 1 a vehicle seat assembly, generally indicated at 10,
`including a vehicle seat, generally indicated at 11, and an
`occupant sensing system, generally indicated at 12. The
`occupant sensing system is particularly adapted to provide
`control signals in an automatic headrest adjustment system
`as described hereinbelow. In general, the occupant sensing
`system 12 senses the location of a head of an occupant on a
`headrest, generally indicated at 14, of the seat 11 in a first
`embodiment of the present invention or the height of the
`occupant shoulder while the occupant is seated in a second
`embodiment of the present invention. In both embodiments,
`a passive transducer array (i.e. pressure transducers, or force
`sensing resistors) is used for sensing.
`The vehicle seat 11 includes seat back and bottom cush(cid:173)
`ions 16 and 18, respectively, to support corresponding back
`and bottom parts of an occupant seated on the vehicle seat
`
`9
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`40
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`5
`11. The headrest 14 includes a headrest cushion 20 which
`has a variable height relative to the bottom cushion 18.
`In the first embodiment and referring to FIGS. 1 and 2, the
`occupant sensing system 12 for use in the automatic headrest
`adjusting system includes a passive transducer array in the 5
`form of pressure transducers such as force sensing resistors
`22 which are vertically spaced apart from one another in the
`headrest cushion 20. The transducers 22 detect pressure
`caused by the head of the occupant pressing on the headrest
`and generate corresponding electrical output signals. 10
`Typically, a minimum of three vertically spaced transducers
`22 are required to sense the location of the occupant's head
`with respect to the headrest 14.
`The assembly 10 also includes a controller 24 which is
`coupled to the transducers 22 to receive and process the
`electrical output signals therefrom and for generating an 15
`electrical control signal. The controller 24 typically includes
`a microcontroller such as a crisp or fuzzy logic processor
`which takes the output signals from the transducers 22 and
`evaluates them with a set of predefined rules. The output
`control signal from the controller 24 then typically drives a 20
`bidirectional headrest adjusting motor 26 which is coupled
`to the headrest 14. Preferably, the headrest adjusting motor
`26 is a stepper motor and is controlled from the controller
`24. Also, preferably, the stepper motor is controlled by the
`controller 24 in an open loop fashion.
`The signals from the transducers 22 are typically condi(cid:173)
`tioned by a conditioning circuit (not shown) prior to being
`input into the controller 24. Typically, the controller 24
`scales the input signals and provides a scaled output control
`signal for use to control the motor 26.
`The basic sensing algorithm is defined in Table 1 below.
`S1, S2 and S3 (i.e. transducers 22) constitute a linear
`transducer array. S1 is the uppermost transducer, S2 is the
`middle transducer, and S3 is the lowermost transducer, as 35
`illustrated in FIG. 2.
`If no pressure is applied on the transducer array (i.e. the
`head of the occupant is not contacting at the certain spots of
`the headrest 14), the output is defined as L. If the head of the
`occupant is contacting the headrest 14 at a particular spot
`and the contact pressure is above a pre-defined threshold, the
`output of the transducers 22 is defined as H.
`
`6
`The vehicle seat 11 is preferably an integrated restraint
`seat in that a seat belt 34 is either incorporated in the
`headrest 14 or in a separate part of the vehicle seat 11 which
`travels with the headrest 14. In a normal driving position, the
`shoulder blade of the occupant generates a distinguishably
`higher pressure on the seat back cushion 16 at certain spots,
`as illustrated in FIGS. Sb and 6b. For example, FIGS. Sa and
`Sb illustrate computer-generated images of body pressure
`distributions on bottom and seat back cushions, respectively,
`for one individual. FIG. Sc is a schematic view of a seat
`assembly with alphanumeric characters thereon correspond(cid:173)
`ing to the images of FIGS. Sa, Sb, 6a and 6b. FIGS. 6a and
`6b illustrate computer-generated images of body pressure
`distributions on bottom and seat back cushions, respectively,
`for a second individual. The images of FIGS. Sa and Sb
`represent a taller occupant than the images of FIGS. 6a and
`6b.
`From such body pressure distributions such as illustrated
`in FIGS. Sa and Sb and FIGS. 6a and 6b, one can determine
`the location of those spots in the seat back cushion which are
`related to the height of the occupant. Consequently, by
`embedding the pressure transducers 32 into the seat back
`cushion 16, one can determine the relative height of the
`occupant and the desired height of the headrest 14 and its
`associated seat belt 34.
`Referring now to FIGS. 1, 3, 4 and 7a, the vehicle seat
`assembly 10 also includes an occupant sensing system,
`generally indicated at 40, including a first occupant sensing
`sensor or transducer 42 mounted in the seat back cushion 16
`to generate a first electrical output signal and a second
`occupant sensing sensor or transducer 44 mounted or
`embedded in the bottom cushion 18 to generate a second
`electrical output signal in response to pressure caused by the
`occupant seated in the vehicle seat 11. Preferably, each of the
`sensors 42 and 44 is either a force sensing resistor or a
`mechanical switching device. When the occupant sensors 42
`and 44 are embodied as mechanical switches, the occupant
`sensor typically comprises a slide-type switch having upper
`and lower rails and an insulator disposed therebetween.
`A second sensor 42' is preferably provided together with
`the sensor 42 so that together the sensors 42 and 42' can
`sense the height of the lowest shoulder blade point of a
`female as well as the height of the highest shoulder blade
`point of a male to collectively generate an electrical output
`signal to thereby obtain a sitting acromial height. While the
`second sensor 42' is not hereinafter specifically mentioned,
`it is to be understood that, preferably, when the sensor 42 is
`mentioned, the sensor 42' is also implied.
`50 When the sensors 42 and 44 are embodied as transducers,
`a minimum of two transducers T1, T2 (i.e. sensors 42 and 44
`Still referring to FIGS. 1 and 2, a second embodiment of
`of FIG. 7a) are required to sense the presence of the
`the vehicle seat assembly 10 includes a second passive
`occupant. One transducer 44 is placed on the bottom cushion
`transducer array, generally indicated at 30, substantially
`18 and the other transducer 42 is placed on the seat back
`identical to the array in the cushion 20. The array 30,
`55 cushion 16. The transducers 42 and 44 are embedded in the
`however, is mounted in the seat back cushion 16 to detect
`trim and no other parts are exposed to the seat surface.
`pressure caused by the occupant's back on the seat back
`The output of each of the transducers 42 and 44 is coupled
`cushion 16. The passive transducer array 30 includes pres(cid:173)
`to the controller 24 through a signal conditioning circuit (not
`sure transducers also in the form of force sensing resistors 32
`shown). The controller 24 receives and processes the signals
`to detect a location of at least one acromion or outer upper
`part of the shoulder blade or scapula of an occupant seated 60 from the transducers 42 and 44 periodically. A resulting
`output control signal from the controller 24 is connected to
`on the vehicle seat 11. In general, sensing the sitting acro(cid:173)
`air bag ignition or actuation circuit 48 which controls air bag
`mial height of an individual provides sufficient information
`deployment on the passenger side assuming that the seat 11
`about the approximate location of an occupant's head so that
`is a passenger side seat.
`the controller 24 can controllably adjust the headrest 14
`Referring to FIG. 2, when the seat is occupied, both
`through the motor 26. In other words, information is readily 65
`available which correlates the average person's shoulder
`transducers 42 and 44 are activated and generate a logical1
`blade height with the height of the person's head.
`(high) signal at the output (Table 2 below). If a rear-facing
`
`TABLE 1
`
`S1
`
`H
`L
`L
`
`S2
`
`L
`H
`L
`
`S3
`
`L
`L
`H
`
`45
`
`Location of the headrest
`
`Headrest is too low
`Headrest is appropriate
`Headrest is too high
`
`10
`
`

`
`5,848,661
`
`7
`child seat is mounted on the seat 11 (i.e. FIG. 3 with respect
`to an instrument panel19), only the transducer 44 (T1) at the
`bottom cushion 18 will activate (logic 1, high). Since there
`is no pressure applied on the seat back cushion 16, trans(cid:173)
`ducer 42 (T2) will not be activated (logic 0, low). The output
`from the controller 24 will become low and turn off the air
`bag. If neither an occupant nor a forward-facing child seat
`is present, the output of the logic remains low.
`Consequently, this system
`can distinguish an occupant
`It will help to prevent an 10
`from rear-facing child seat.
`improper deploying air bag.
`
`TABLE 2
`
`T1
`(Sensor 44)
`
`T2
`(Sensor 42)
`
`Air
`Output Bag
`
`0
`
`0
`0
`
`0
`0
`
`OFF
`OFF
`
`ON
`
`Scenario
`
`Nothing in the seat
`Rear-facing child seat
`in the seat
`Occupant or forward- facing
`child seat (i.e. FIG. 4)
`
`15
`
`20
`
`8
`delay is entered at block 56 (i.e. there was an occupant
`previously seated on the cushions).
`At block 58, if the delay reaches a predetermined amount
`of time such as 5 seconds, then the logic reverts back to the
`5 beginning before block 50. However, if a delay has not
`timed out at block 58, then block 52 is re-entered and the
`signals from the first and second cushions 18 and 16,
`respectively, are again tested. Blocks 52, 54 and 58 take into
`account a special condition. For example, a car can hit a
`bump so that the occupant involuntarily leaves the seat or the
`occupant can voluntarily leave his/her seating position on
`the seat.
`At block 60, after it has been determined that one of the
`transducers in one of the cushions 16 or 18 is sensing a
`predetermined pressure, then it is tested if the first cushion
`18 has a high pressure and the second cushion 16 has a low
`pressure.
`At block 62, if the determination at block 60 is positive,
`then the air bag latch flag is tested to see whether it is "on."
`If it is "on," (i.e. there was an occupant) then the algorithm
`proceeds again to block 52. If the air bag latch flag at block
`62 is not "on," then the air bag control signal should be
`emitted to turn the air bag actuation circuit 48 "off" at block
`64.
`If the decision at block 60 is negative, then at block 66 it
`is determined whether both sensors in the top and lower
`cushions are experiencing pressure. If not, then logic at
`block 52 is again entered.
`If the transducers are both experiencing pressure as tested
`at block 66, then at block 68, the air bag actuation circuit 48
`should be turned "on," and, at block 70, the air bag latch flag
`should be set high. After block 70, then logic at block 52 is
`again reentered.
`The occupant sensing algorithm illustrated by the flow
`35 chart of FIG. 7b takes into account each of the following
`scenanos:
`
`Referring now to FIG. 7b, there is illustrated a block
`diagram flow chart for the control logic contained within the
`controller 24 for distinguishing between a properly seated 25
`occupant and a rear-facing infant seat, and certain special
`conditions (i.e. occupant is leaning forward), as illustrated in
`FIG. 3. In general, the control logic distinguishes between a
`properly seated occupant and a rear-facing infant seat based
`on duration and frequency (i.e., patterns) of a first electrical 30
`output signal from the occupant sensor 42 (i.e. T2).
`The following terminology is applicable to the flow chart
`of FIG. 7b:
`AB=O=Air Bag Off;
`AB=1=Air Bag On;
`Sensor 44=L-No pressure on Cushion #1 (i.e. 18);
`
`1.
`
`2.
`
`3.
`
`Power on ___,. No occupant
`Tl~L,T2~LAB~<j>
`Power on ___,. No occupant ___,. Occupant presence (seat not normal)
`Tl~L,T2~LT1~H,T2~L AB~<j>
`Power on ___,. No occupant ___,. Occupant presence (seat normal)
`Tl~L,T2~LT1~H,T2~H AB~1
`Power on ~ No occupant ~ Occupant (seat normal) ~ Occupant (seat not normal)
`Tl~L,T2~LT1~H,T2~H
`Tl~H,T2~L AB~1
`5. Occupant presence (seat normal) ~ Power on
`
`4.
`
`6.
`
`Power on ___,. Occupant (seat normal) ___,. No occupant ___,.
`Tl~H,T2~H
`Tl~L,T2~L
`F~1~AB~<j>
`
`Rear-facing child seat
`Tl~H,T2~L
`F"1
`AB~O
`
`8.
`
`7. Rear-facing child seat___,. Power on
`Tl~L,T2~L
`AB~O
`Front-facing child seat ___,. Power on
`Tl~H,T2~H
`AB~1
`Power on~ Occupant(None) ~ Occupant Moved~ Occupant
`AB~1
`Tl~L
`AB~1
`T2 ~ L
`
`9.
`
`Sensor 44=H-Detectable pressure presence on Cushion #1;
`Sensor 42=L-No pressure on Cushion #2 (i.e. 16);
`Sensor 42=H-Pressure presence on Cushion #2; and
`F=Air Bag on Latch Flag.
`Referring again to FIG. 7b, at block 50, the air bag is off
`and the air bag latch flag is 0.
`At block 52, it is tested to determine whether there is any
`pressure on either of transducers 44 or 42.
`At block 54, if there is no pressure on either of cushions
`1 or 2 and the air bag latch flag is set, then a predetermined
`
`While the best mode for carrying out the invention has
`been described in detail, those familiar with the art to which
`60 this invention relates will recognize various alternative
`designs and embodiments for practicing the invention as
`defined by the following claims.
`What is claimed is:
`1. A vehicle seat assembly comprising:
`a vehicle seat including seat back and bottom cushions to
`support corresponding back and bottom parts of an
`occupant seated on the vehicle seat and a headrest
`
`65
`
`11
`
`

`
`5,848,661
`
`9
`having a headrest cushion with a variable height rela(cid:173)
`tive to the bottom cushion;
`an occupant-sensing system including a passive trans(cid:173)
`ducer array including a plurality of vertically-spaced
`transducers mounted in one of the seat back and 5
`headrest cushions to detect pressure caused by the
`occupant seated on the vehicle seat and to generate
`corresponding electrical output signals; and
`a controller coupled to the passive transducer array for
`processing the electrical output signals and generating 10
`an electrical control signal adapted to automatically
`control a motor coupled to the headrest to adjust the
`variable height of the headrest cushion based on dis(cid:173)
`tribution of body pressure caused by the occupant
`seated on the vehicle seat detected by the vertically- 15
`spaced transducers.
`2. The assembly as claimed in claim 1 wherein the passive
`transducer array is mounted in the headrest cushion to detect
`location of a head of the occupant seated on the vehicle seat
`relative to the headrest and wherein the controller generates 20
`the control signal based on a seating height of the occupant
`seated on the vehicle seat.
`3. The assembly as claimed in claim 1 wherein the passive
`transducer array includes three vertically spaced pressure
`transducers.
`4. The assembly as claimed in claim 3 wherein the
`pressure transducers are force-sensing resistors.
`5. The assembly as claimed in claim 2 further comprising
`a seat belt coupled to the