Title: Vehicle occupant sensing system having sensor assemblies with variable blasing member
Abstract: A vehicle occupant sensing system that includes a sensor assembly. The sensor assembly has a housing that includes a base and an upper slide member. The upper slide member is moveable toward and away from the base. A sensor is operatively fixed relative to at least one of the upper slide member and the base and is operable to detect movement of the upper slide member toward and away from the base. Additionally, the vehicle occupant sensing system includes a variable biasing member adapted to bias the upper slide member away from the base with a force that is non-linearly related to movement of the upper slide member toward and away from the base. The vehicle occupant sensing system of the present invention may be employed in a vehicle seat assembly to detect a condition of the vehicle seat assembly.
Patent Number: 6,994,397 Issued on 02/07/2006 to Young, et al.
| Inventors:
|
Young; Oliver J. (Grosse Pointe Farms, MI);
Nathan; John F. (White Lake Township, MI)
|
| Assignee:
|
Lear Corporation (Southfield, MI)
|
| Appl. No.:
|
848266 |
| Filed:
|
May 18, 2004 |
| Current U.S. Class: |
297/217.2; 297/217.3; 297/463.2; 280/735 |
| Current Intern'l Class: |
A47C 31/12 (20060101); A47C 7/62 (20060101) |
| Field of Search: |
297/2172,217.3,463.2
280/735
|
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Primary Examiner: White; Rodney B.
Attorney, Agent or Firm: Bliss McGlynn, P.C., Panagos; Bill
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation-in-part of U.S. Ser. No. 10/748,536, entitled
"Vehicle Occupant Sensing System Having a Low Profile Sensor Assembly" and filed
Dec. 30, 2003, which is a continuation-in-part of U.S. Ser. No. 10/606,649, entitled
"Encapsulated Spring Sensor Assembly" and filed Jun. 26, 2003.
Claims
What is claimed is:
1. A vehicle seat assembly comprising:
a seat cushion defining an upper surface and a lower surface spaced from said
upper surface; and
a vehicle occupant sensing system including:
a plurality of sensor assemblies, each of said sensor assemblies disposed below
said seat cushion adjacent said lower surface, said sensor assemblies each having
a housing that includes a base and an upper slide member, said upper slide member
moveable toward and away from said base and responsive to movement of said upper
surface of said seat cushion toward said lower surface of said seat cushion thereby
responding to the presence of an occupant in said vehicle seat;
a sensor operatively fixed relative to at least one of said upper slide member
and said base and operable to detect movement of said upper slide member toward
and away from said base in response to the presence of an occupant in said vehicle
seat; and
a variable biasing member adapted to bias said upper slide member away from said
base with a force that is non-linearly related to movement of said upper slide
member toward and away from said base, wherein said variable biasing member includes
a plurality of sections of which at least two of said sections exhibit different
spring rates.
2. A vehicle seat assembly as set forth in claim 1, wherein at least two of said
sections have different spring pitches.
3. A vehicle seat assembly as set forth in claim 1, wherein said variable biasing
member includes a low rate section at each end and a high rate section between
said low rate sections.
4. A vehicle seat assembly as set forth in claim 1, wherein said variable biasing
member is a stiffening spring.
5. A vehicle seat assembly as set forth in claim 1, wherein said variable biasing
member is a coiled spring operatively disposed between said base and said upper
slide member.
6. A vehicle seat assemby as set forth claim 1, wherein said sensor is operable
to detect a change in magnetic flux density generated by movement of said upper
slide member toward and away from said base.
7. A vehicle seat assembly as set forth in claim 1, wherein said sensor assembly
further comprises an intermediate guide member disposed between said upper slide
member and said base, said intermediate guide member moveable toward and away from
said base.
8. A vehicle seat assembly as set forth in claim 1, wherein said upper slide
member includes a lower flange that defines the limit of movement of said upper
slide member away from said base, and wherein said lower flange facilitates axial
movement of said upper slide member relative to said base.
9. A vehicle seat assembly as set forth in claim 8, wherein said base includes
an inner platform that is adapted to accept said lower flange of said upper slide
member when said upper slide member moves toward said base.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to vehicle occupant sensing systems and,
more particularly, to a vehicle occupant sensing system having sensor assemblies
with a variable biasing member.
2. Description of the Related Art
Automotive vehicles employ seating systems that accommodate the passengers
of the vehicle. The seating systems include restraint systems that are calculated
to restrain and protect the occupants in the event of a collision. The primary
restraint system commonly employed in most vehicles today is the seatbelt. Seatbelts
usually include a lap belt and a shoulder belt that extends diagonally across the
occupant's torso from one end of the lap belt to a mounting structure located proximate
to the occupant's opposite shoulder.
In addition, automotive vehicles may include supplemental restraint systems.
The
most common supplemental restraint system employed in automotive vehicles today
is the inflatable airbag. In the event of a collision, the airbags are deployed
as an additional means of restraining and protecting the occupants of the vehicle.
Originally, the supplemental inflatable restraints (airbags) were deployed in the
event of a collision whether or not any given seat was occupied. These supplemental
inflatable restraints and their associated deployment systems are expensive and
over time this deployment strategy was deemed not to be cost effective. Thus, there
became a recognized need in the art for a means to selectively control the deployment
of the airbags such that deployment occurs only when the seat is occupied.
Partially in response to this need, vehicle safety systems have been proposed
that include vehicle occupant sensing systems capable of detecting whether or not
a given seat is occupied. The systems act as a switch in controlling the deployment
of a corresponding air bag. As such, if the occupant sensing device detects that
a seat is unoccupied during a collision, it can prevent the corresponding air bag
from deploying, thereby saving the vehicle owner the unnecessary cost of replacing
the expended air bag.
Furthermore, many airbag deployment forces and speeds have generally
been optimized to restrain one hundred eighty pound males because the one hundred
eighty pound male represents the mean average for all types of vehicle occupants.
However, the airbag deployment force and speed required to restrain a one hundred
eighty pound male exceeds that which are required to restrain smaller occupants,
such as some females and small children. Thus, there became a recognized need in
the art for occupant sensing systems that could be used to selectively control
the deployment of the airbags when a person below a predetermined weight occupies
the seat.
Accordingly, other vehicle safety systems have been proposed that are
capable of detecting the weight of an occupant. In one such air bag system, if
the occupant's weight falls below a predetermined level, then the system can suppress
the inflation of the air bag or will prevent the air bag from deploying at all.
This reduces the risk of injury that the inflating air bag could otherwise cause
to the smaller-sized occupant.
Also, many airbag deployment forces and speeds have generally been optimized
to restrain a person sitting generally upright towards the back of the seat. However,
the airbag deployment force and speed may inappropriately restrain a person sitting
otherwise. Thus, there became a recognized need in the art for a way to selectively
control the deployment of an airbag depending on the occupant's sitting position.
Partially in response to this need, other vehicle safety systems have been
proposed that are capable of detecting the position of an occupant within a seat.
For example, if the system detects that the occupant is positioned toward the front
of the seat, the system will suppress the inflation of the air bag or will prevent
the air bag from deploying at all. This reduces the risk of injury that the inflating
air bag could otherwise cause to the occupant.
It can be appreciated that these occupant sensing systems provide valuable data,
allowing the vehicle safety systems to function more effectively to reduce injuries
to vehicle occupants.
One necessary component of each of the known systems discussed above includes
some means for sensing the presence of the vehicle occupant in the seat. One such
means may include a sensor device supported within the lower seat cushion of the
vehicle seat. For example, U.S. published patent application having U.S. Ser. No.
10/249,527 and Publication No. US2003/0196495 A1 filed in the name of Saunders
et al. discloses a method and apparatus for sensing seat occupancy including a
sensor/emitter pair that is supported within a preassembled one-piece cylinder-shaped
housing. The housing is adapted to be mounted within a hole formed in the seat
cushion and extending from the B-surface toward the A-surface of the seat cushion.
The sensor/emitter pair supported in the housing includes an emitter that is mounted
within the seat cushion and spaced below the upper or A-surface of the seat cushion.
In addition, the sensor is also supported by the housing within the seat cushion
but spaced below the emitter. The cylindrical housing is formed of a compressible,
rubber-like material that is responsive to loads placed on the upper surface of
the seat cushion. The housing compresses in response to a load on the seat cushion.
The load is detected through movement of the emitter toward the sensor as the housing
is compressed. The housing is sufficiently resilient to restore the emitter to
full height when no load is applied to the upper surface of the seat cushion. The
Saunders et al. system also includes a processor for receiving the sensor signals
and interpreting the signals to produce an output to indicate the presence of an
occupant in the seat.
While the Saunders et al. occupant seat sensing system teaches a sensor/emitter
pair that may sense the presence of a vehicle seat occupant, it suffers from certain
disadvantages associated with the fact that it is mounted within the seat cushion
of the vehicle seat. For example, vehicle seat cushions typically employ a foam
or other cushiony material of a predetermined thickness. The thickness of this
material is preferably calculated to provide adequate comfort for the occupant.
However, with the housings of the sensor/emitter pairs mounted within the cushion,
the occupant may feel one or more of the housings through the seat cushion. This
is especially true over time as the seat cushion becomes worn. Furthermore, while
the compressible, rubber-like housing taught by Saunders et al. is generally responsive
to forces extending along the length of its axis, is also subject to transverse
or "shear" forces acting through the seat cushion. Thus, the housing can be deformed
in an irregular manner resulting in false readings generated by the sensor/emitter pair.
Therefore, there is an ongoing need in the art for a vehicle occupant
sensing system including a low profile sensor assembly that can provide suitable
occupant sensing capabilities and yet be positioned outside the envelope defined
by the lower seat cushion without detrimentally affecting the comfort level of
the seat. Furthermore, there is a need in the art for such a vehicle occupant sensing
system that is resistant to shear forces and otherwise constructed to respond in
a single axis of movement.
Furthermore, the stiffness of the housing of the Saunders et al. device
can disadvantageously limit the system's responsiveness. For instance, if a lighter
occupant sits on the seat cushion, an overly stiff housing may not deflect enough
and thereby inhibit the sensor/emitter pair from generating a responsive signal.
As such, the system cannot gather data for occupants that are at or below a certain
weight limit. On the other hand, if a heavier occupant sits on the seat cushion,
an overly elastic housing may deflect too much, allowing the sensor and emitter
to contact each other. As such, the system cannot distinguish between occupants
that are at or above a certain weight limit, and contact between the sensor and
emitter can cause premature wear.
Overall, the system may not appropriately sense the presence of some occupants
because of these limitations in system responsiveness. Accordingly, there remains
a need in the art for a vehicle occupant sensing system that is responsive to a
wider occupant weight range.
SUMMARY OF THE INVENTION
The present invention overcomes the disadvantages in the related art in a vehicle
occupant sensing system that includes a sensor assembly. The sensor assembly has
a housing that includes a base and an upper slide member. The upper slide member
is moveable toward and away from the base. A sensor is operatively fixed relative
to at least one of the upper slide member and the base and acts to detect movement
of the upper slide member toward and away from the base. Additionally, the vehicle
occupant sensing system includes a variable biasing member adapted to bias the
upper slide member away from the base with a force that is non-linearly related
to movement of the upper slide member toward and away from the base. The vehicle
occupant sensing system of the present invention may be employed in a vehicle seat
assembly to detect a condition of the vehicle seat assembly.
The variable biasing member preferably exhibits an appropriate stiffness for
both lighter and heavier occupants of the vehicle seat assembly. For instance,
when a lighter occupant sits on the seat assembly, the variable biasing member
preferably deflects enough to cause correlating data to be generated. However,
when a heavier occupant sits on the seat cushion, the variable biasing member is
preferably stiff enough to allow deflection without the variable biasing member
reaching a solid height, thereby allowing correlating data to be further generated.
Thus, the variable biasing member allows data to be generated for lighter occupants
and for heavier occupants, thereby making the vehicle occupant sensing system more
responsive to a wider occupant weight range.
Other features and advantages of the present invention will be readily appreciated,
as the same becomes better understood, after reading the subsequent description
taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an exploded view of a vehicle seat assembly incorporating a vehicle
occupant sensing system having a plurality of low profile sensor assemblies;
FIG. 2 is an exploded view of one embodiment of the low profile sensor assembly
suitable for use in the vehicle occupant sensing system illustrated in FIG. 1;
FIG. 3 is a cross-sectional side view of the low profile sensor assembly of
FIG. 2 shown in a free state;
FIG. 4 is a cross-sectional side view of the low profile sensor assembly of
FIG. 2 shown in a compressed state;
FIG. 5 is an exploded view of another embodiment of the low profile sensor assembly
suitable for use in the vehicle occupant sensing system illustrated in FIG. 1;
FIG. 6 is a cross-sectional side view of the low profile sensor assembly of
FIG. 5 shown in a free state;
FIG. 7 is a cross-sectional side view of the low profile sensor assembly of
FIG. 5 shown in a compressed state;
FIG. 8 is a side view of one embodiment of a variable biasing member of the
present invention; and
FIG. 9 is a graph depicting response from one embodiment of the variable biasing member.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
Referring now to the drawings, where like numerals are used to designate
like structure throughout the figures, an exploded view of one embodiment of the
vehicle seat assembly of the present invention is generally indicated at
10
in FIG.
1. The vehicle seat assembly
10 includes a seat back, generally
indicated at
12, and a lower seat assembly, generally indicated at
14.
The lower seat assembly
14 has a seat cushion
16 that defines an
upper surface
18, and a lower surface
20 that is spaced from the
upper surface
18. The upper surface
18 of the seat cushion
16
may be referred to as the "A-surface" and the lower surface
20 may be referred
to as the "B-surface." The seat cushion
16 also defines an inboard side
22 and an outboard side
24. When an occupant (not shown) is supported
on the lower seat assembly
14, the weight of the occupant will apply an
axial load directed generally through the upper surface
18 of the seat cushion
16 toward the lower surface
20. Although the weight of the occupant
will induce an axial as well as shear forces in the seat cushion
16, those
having ordinary skill in the art will recognize that the primary load path of the
occupant's weight will be substantially vertical from the upper surface
18
toward the lower surface
20, through the seat cushion
16.
The lower seat assembly
14 also includes a seat pan, generally indicated
at
26. The seat pan
26 is generally disposed beneath the lower surface
18 so as to support the seat cushion
16. In turn, the seat pan
26
is operatively supported relative to the floor of the vehicle using any suitable
structure of the type commonly known in the art, such as a seat track (not shown).
In addition, the vehicle seat assembly
10 includes a vehicle occupant sensing
system, generally indicated at
28. The vehicle occupant sensing system
28
is used for detecting a condition of the vehicle seat assembly
10, such
as whether or not the vehicle seat assembly
10 is occupied, whether the
occupant is above or below a certain weight requirement, or whether the occupant
is sitting in a certain position.
The sensing system
28 includes a circuit carrier tray, generally indicated
at
30, that is supported by the seat pan
26. The circuit carrier
tray
30 includes a plurality of resilient attachment tabs
32 extending
upward toward the lower surface
20 of the lower seat cushion
16.
Each attachment tab
32 is shaped like a partial ring that extends upward
from the tray
30. In the preferred embodiment illustrated in FIG. 1, the
attachment tabs
32 are arranged into mirror-image pairs spaced intermittently
about the tray
30. The tray
30 supports components of the vehicle
occupant sensing system
28 as will be described in greater detail below.
The vehicle occupant sensing system
28 also includes a circuit carrier
34, which is disposed adjacent the lower surface
20 of the seat cushion
16. The tray
30 supports the circuit carrier
34, and the circuit
carrier
34 includes a plurality of cutouts
36 each having a shape
corresponding to the shape of the attachment tabs
32 of the tray
30
such that the tabs
32 can extend upward through the circuit carrier
34.
The vehicle occupant sensing system
28 also includes an electric circuit
38, which is supported by the circuit carrier
34. Specifically, the
circuit carrier
34 is made of a thin nonconductive and corrosion-resistant
material, and it encapsulates known electrical components that form the electric
circuit
38. For instance, in one embodiment, a flexible printed circuit
forms the circuit carrier
34 and electric circuit
38.
The circuit
38 is electrically connected to a controller schematically
illustrated at
40. As described in greater detail below, the electric circuit
38 carries electric signals generated by the vehicle occupant sensing system
28 to the controller
40. The controller
40 is electrically
attached to a restraint system, schematically illustrated at
42. The restraint
system
42 can be of many types, such as an air bag system, and the controller
40 sends output to the restraint system
42 based on the signals delivered
by the electric circuit
38. Although an airbag restraint system is discussed
here, one having ordinary skill in the art will recognize that the type of restraint
system
42 connected to the controller
40 does not limit the scope
of the present invention.
The system
28 also includes a plurality of low profile sensor assemblies
44 that are supported by the tray
30, below the lower surface
20
of the seat cushion
16. In one embodiment not shown, the lower surface
20
includes a plurality of depressions, and each of the low profile sensor assemblies
44 are spaced according to a corresponding depression formed in the lower
surface
20 of the lower seat cushion
16. As will be discussed in
greater detail below, the sensor assemblies
44 have a relatively low profile
and can collapse in a more compact manner than similar sensor assemblies of the
prior art. Advantageously, these low profile sensor assemblies
44 allow
an occupant to sit more comfortably upon the vehicle seat
10.
Also, a sensor, generally indicated at
46, is operatively fixed relative
to each of the low profile sensor assemblies
32. The sensor
46 is
in electrical communication with the electric circuit
38. The low profile
sensor assemblies
44 each cooperatively operate with the associated sensor
46 to detect a condition of the vehicle seat
10 as will be described
in greater detail below. For example, the low profile sensor assemblies
44
and sensor
46 can operate to detect that the vehicle seat
10 is unoccupied,
is occupied by a person of a particular weight, or is occupied by a person sitting
in a particular position.
One embodiment of the low profile sensor assembly is generally indicated at
44
and shown in greater detail in FIGS. 2-4. The low profile sensor assembly
44
generally includes a housing
48, having a base
50, an upper slide
member
52, and an intermediate guide member
54 disposed between the
upper slide member
52 and the base
50. The upper slide member
52
and the intermediate guide member
54 are both supported for movement toward
and away from the base
50. A biasing member
56 acts to bias the upper
slide member
52 and intermediate guide member
54 away from the base
50 as will be described in greater detail below.
In the preferred embodiment illustrated in these figures, the base
50
includes
a base guide
58, which is shaped like a hollow tube so as to define a wall
60 with a bore
62 extending axially therethrough. On an outside surface
of the wall
60, two hold-down flanges
64 project radially outward,
spaced 180° apart from each other. An aperture
66 extends radially
through the wall
60 directly above each hold-down flange
64.
The base
50 also includes a retainer
68, which is substantially
disc-shaped and is attached to one terminal end of the base guide
58. Two
resilient tabs
70 extend radially and upward from an outer circumferential
edge of the retainer
68. The tabs
70 are spaced 180° apart from
each other. To connect the retainer
68 and the base guide
58, the
retainer
68 moves axially into the bore
62 of the base guide
58
such that the tabs
70 of the retainer
68 snap into the apertures
66 of the base guide
58.
As shown in FIGS. 3 and 4, the base
50 can be attached to the annular
attachment
tabs
32 that extend upwardly from the tray
30. Specifically, the
hold-down flanges
64 of the base guide
58 can be positioned under
the annular attachment tabs
32 of the tray
30 such that the annular
attachment tabs
32 retain the hold-down flanges
64. In one embodiment,
to attach the base
50 to the tray
30, the bottom surface of the base
50 is positioned on the tray
30 such that the hold-down flanges
64
and the annular attachment tabs
32 are not aligned. Then, the base
50
is rotated about its axis until the hold-down flanges
64 move completely
under the annular attachment tabs
32. In another embodiment, the hold-down
flanges
64 and the annular attachment tabs
32 are aligned, and the
base
50 is moved axially toward the tray
30 such that the annular
attachment tabs
32 bend back and snap over the hold-down flanges
64.
Also, an annular void
72 is formed near the axial center of the base
50. In one embodiment shown in FIGS. 3 and 4, the sensor
46 is a
Hall effect sensor attached to the circuit carrier
34 between each pair
of tabs
32 of the tray
30. Electrical attachment between the sensor
46 and the circuit carrier
34 can be accomplished in the manner described
in applicant's co-pending application, Ser. No. 10/748,514, entitled "Vehicle Occupant
Sensing System and Method of Electrically Attaching a Sensor to an Electrical Circuit,"
which is hereby incorporated in its entirety by reference. When the base
50
is attached to the tray
30, the annular void
72 provides clearance
for the sensor
46.
The retainer
68 has a top surface
74, which is stepped so as define
a plurality of concentric features. First, the stepped top surface
74 defines
an outer step
76 formed on the outer radial portion of the top surface
74
of the retainer
68. Next, the stepped top surface
74 defines an inner
platform
78 formed radially inboard of the outer step
76. As shown
in FIGS. 3 and 4, the inner platform
78 extends axially upward from the
outer step
76. Finally, nearest the center of the stepped top surface
74
is a ring
80 extending upward from the inner platform
78.
As noted above, the low profile sensor assembly
44 includes an upper slide
member
52. The upper slide member
52 includes an upper disc portion
82 and a support wall
84 extending axially downward from the outer
circumference of the upper disc portion
82. The support wall
84 has
a smaller diameter than the diameter of the intermediate guide member
54
such that the upper slide member
52 can move axially through the intermediate
guide member
54. The biasing member
56 is disposed between the inner
platform
78 of the base
50 and the upper disc portion
82 of
the upper slide member
52.
As noted above, the low profile sensor assembly
44 also includes the intermediate
guide member
54, which is substantially tubular so as to define an outer
surface
56 and an inner surface
88. The diameter of the intermediate
guide member
54 is smaller than the diameter of the bore
62 of the
base guide
58 such that the intermediate guide member
54 can move
axially through the bore
62.
The intermediate guide member
54 includes a lower flange
90 formed
on its lower end, and the base
50 includes an upper flange
92 formed
on the upper end of the base guide
58. In the embodiment shown, the lower
flange
90 of the intermediate guide member
54 extends radially outward,
and the upper flange
72 of the base
50 extends radially inward. The
diameter of the lower flange
90 is larger than the diameter of the upper
flange
92. As such, the intermediate guide member
54 can be positioned
within the bore
62 of the base guide
58. As the lower flange
90
of the intermediate guide member
54 slides toward the upper flange
92,
the upper flange
92 interferes with the lower flange
90, thereby
inhibiting further upward movement of the intermediate guide member
54.
Thus, the upper flange
92 on the base
50 and the lower flange
90
on the intermediate guide member
54 cooperate to define the limit of sliding
movement of the intermediate guide member
54 away from the base
50.
While the upper flange
92 of the base
50 defines one limit of
travel of the intermediate guide member
54, the outer step
76 of
the base
50 defines the other limit of travel. As shown specifically in
FIG. 4, the intermediate guide member
54 can move axially downward within
the base
50 until the lower flange
90 of the intermediate guide member
54 contacts the outer step
76 of the base
50. Thus, the outer
step
76 is adapted to accept the lower flange
90 of the intermediate
guide member
54 when the intermediate guide member
54 moves toward
the base
50, and it defines the axial limit of travel of the intermediate
guide member
54 toward the base
50. It is noted that since the outer
step
76 is formed at a lower level than the inner platform
78 of
the base
50, the intermediate guide member
54 has a greater range
of motion in the axial direction. As such, the sensor assembly
44 has a
lower profile than other sensors known in the related art and can collapse into
a more compact arrangement, thereby making the sensor assembly
44 less likely
to detrimentally affect the comfort of the vehicle seat
10.
In the preferred embodiment, the base
50 defines an inner guide surface
94. The inner guide surface
94 is formed on the inner surface of
the wall
60 of the base guide
58, and it has a diameter slightly
larger than the diameter of the lower flange
90 of the intermediate guide
member
54. The inner guide surface
94 substantially guides the lower
flange
90 as it slides within the base
50, such that the intermediate
guide member
54 slides in a substantially axial direction. Thus, the lower
flange
90 of the intermediate guide member
54 cooperates with the
inner guide surface
94 of the base
50 to facilitate movement of the
intermediate guide member
54 relative to the base
50 in a substantially
axial direction. By guiding the intermediate guide member
54 in a substantially
axial direction, the sensor
46 is adapted to generate more accurate readings
as will be
