Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
J~ t;i~
1 ~ne of -the devices intended to protect a vehicle's
2¦ occupant against injury is an instrumentality such as an in-
3 ¦flatable airbag which is house~ in the passenger compartment
4 forwardly of the occupan-t in a deflated condition. When such
5 ¦vehicle is subjected to acceleration of the kind accompanying
61 a crash, the airbag inflates to provide a protective cushion
7 ¦for the occupant.
81
When a moving vehicle becomes involved in a crash
10 ¦ of such severity as to slow or stop the vehicle suddenly, an
11 occupant of the vehicle will continue forward movement at the
12 rate the vehicle was traveling at the time of the crash until
13 such time as the occupant collides with some portion of the
14 structure of the passenger compartment. If serious injury to
the occupant is to be prevented, the airbag must be fully
16 inflated before a collision occurs between the occupant and
17 some structure of the passenger compartment. It has been
18 found that, typically, the driver of a vehicle can move
19 forwardly only about five inches from the driving position
before a restraining device such as an airbag is needed to
21 prevent injury. All airbag inflating mechanisms require a
22 period of time, such as thirty milliseconds, to effect in-
23 flation of the airbag once a signal initiating inflation has
24 been received from a sensor. Under these circumstances, an
airbag pxotective device, to be effective, must become in-
~6 flated thirty milliseconds before the occupant has moved
27 five inches from the position he occupied at the time of
28 the crash.
2~
~0 It has been determined that a passenger protective
Y ~
l ¦device is needed when the movement of the vehicle occupant
2 ¦relative to the vehicle is at a velocity of about twelve
3 miles per hour. Thus, an ideal sensor is one which will
4 determine that the occupan-t will collide with some portion
51 of the vehicle's interior at a speed of twelve miles per
6 hour or greater, and thirty milliseconds before the occupant
7 has moved forwardly five inches.
9 ¦ Since an airbag protective device is one which is
designed to prevent forcible collision between a vehicle oc-
11 cupant and some portion of the passenger compartment, it is
12¦ important that the sensor which initiates operation of the air-
13¦ bag inflation mechanism be one which is responsive to the ac-
14¦ celeration of the passenger compartment, rather than some
other part of the vehicle. Not all crashes, however, result
16¦ in acceleration of the vehicle's passenger compartment to a
17 ¦ degree necessary to require operation of the airbag. For ex-
18 ample, if a front fender or bumper of a vehicle should collide
19¦ with a pole or the like which breaks upon or shortly after
20¦ impact, a sensor mounted on the front fender or bumper could
21¦ experience a velocity change of twelve miles per hour, or
22¦ greater, before the pole breaks, whereas the passenger com-
23 partment of the vehicle might experience a negligible velocity
24 change. Under these circumstances, inflation of the airbag
25 ¦would not be required and, if it were, it might even contribute
261 to a subsequent accident. It is important, therefore, that
27 the sensor or sensors with which a vehicle is equipped be lo-
28 ¦cated in such positions and be of such construction as to be
2~ Ipredictive that the passenger compartment will undergo a
~0 ¦velocity change necessitating passenger protection.
F'rontal portions of the vehicle, i.e., bumpers,
2 fenders, radiators, and the like, may undergo a substantial
3 ¦velocity change relative to the passenger compartment inasmuch
4 las such frontal portions of a vehicle are capable of
5 ¦collapsing and absorbing energy. ThuS, sensors mounted at
~ ¦frontal positions on a vehicle should have characteristics
7 ¦different from sensors mounted on its firewall, for example,
8 lin order to assure inflation of an airbag when required, but
9 ¦to avoid inflation cf the airbag in those instances in which
it is not necessary.
11
12 In those sensors which initiate inflation of an
13 airbag via an electrical circuit which requires the closing
14~ for a finite period of time a normally open switch, care must
be taken to ensure that the switch will remain closed, not
16 only for the minimum time required to effect circuit completion,
17¦ but also for a somewhat longer period of time so as to provide
18¦ a factor of safety. In sensors which utilize a biasing mass
19¦ to establish an acceleration threshold which must be exceeded
20 ¦ before closing of the switch is possible, there is a likelihood
21¦ that the biasing mass may move to a position in which the
22¦ switch operating means is free to move toward switch closing
23 position, but then rebound into the path of movemen-t of the
241 switch closing means and delay or prevent closing of the switch,
251 or effect premature reopening of the switch. On the other
26¦ hand, in some instances it may be desirable to delay closing
27 ¦ of the switch for a predetermined period of time so as to
28¦ avoid initiating operation of the airbag until sufficient time
2~ has lapsed to ensure that the circumstances necessitate airbag
3~¦ inflation.
.'Y~1~2~
1 Sensors construc-ted accordlng to -the invention are
2¦ so designed as to enable them to be mounted in selected posi-
31 tions on a vehicle and sense velocity changes which require
4 and do not require actuation of a passenger protective device.
51 A sensor constructed in accordance with the
¦ 6 invention embodies many of the principles disclosed in United
States Patent No. 3,97~,350, granted August 10, 1976, and
8 comprises a body adapted to be mounted on a vehicle or the
like in a position to sense and respond to acceleration pulses.
Within a tubular passage in the body is mounted an acceleration
11 sensing mass formed of electrically conduc-tive material. The
12 sensing mass is movable in response to an acceleration pulse
13 from an initial position along a path leading to a normally
14¦ open switch that is connected via suitable wiring to the
15¦ operating mechanism of an inflatable airbag.
16¦ Biasing means acts on the sensing mass to bias
17¦ the latter to its initial position under a preselected force
18 which must be exceeded before the sensing mass may move from
19¦ its initial position. The biasing means includes a mass
20¦ which normally engages and maintains the sensing mass in its
21¦ initial position, but which moves out of engagement with the
22 sensing mass in response to acceleration greater than the
23 preselected biasing force, thereby freeing the latter for
241 movement toward the switch. Movement of the sensing mass is
251 fluid damped, either inertially or viscously. As thus far
26¦ described, the apparatus disclosed herein is quite similar
27 ¦ in function to that disclosed in the aforementioned patent.
28¦ Movement of the biasing mass in response to
20¦ acceleration is along a linear path, but cooperable means
~0 carried by the body and the biasing mass damp movement of
_ 4 _
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1¦ the la-tter by transla-ting linear movement inko rotary movement
21 and dissipating some of the kinetic energy of the biasing mass.
3 Dissipation of kinetic energy prevents rehounding of the latter
4 into premature reengagement with the sensing mass. The means
51 for translating linear movemen-t of the biasing mass in-to
81 rotary movement may also function to delay movement of the
7 sensing mass into engagement with the switch.
8 1
9 Figure 1 is an enlarged, elevational view of a
casing or housing within which a sensor constructed in
11 accordance with the invention is contained;
12¦ Figure 2 is a horizontal sectional view of a
13 sensor constructed in accordance with one embodiment of
14 the invention;
Figure 3 is a side elevational view, partly
16¦ broken away, of the sensor shown in Figure 2;
17¦ Figure 4 is a sectional view taken on the line
18¦ 4-4 of Figure 3;
19¦ Figure 5 is an elevational view of a detail as
20 ¦ viewed in the direction of the arrows 5-5 of Figure 4; and
21¦ Figure 6 is a view similar to Figure 2, but
22¦ illustrating a modified form of the invention.
23
24¦ A sensor constructed in accordance with the
251 invention is adapted to be enclosed within a sturdy casing or
26¦ housing 1 having flanges 2 provided with openings for the
27 ¦accommodation of screws or the like (not shown) to mount
28¦ the housing at a suitable lo-ation on and relative to the
2~ ¦longitudinal axis of a vehicle. A bushing 3 fits within
3~ ¦ and closes an opening formed in the housing 1 and accommodates
~ 72~
1¦ an insulated cable ~ containing electrical wiring -to be
21 described hereinafter. The housing 1 has a cavity therein
3 for the accommodation of a sensor.
41
51 A sensor constructed according to the embodiment
shown in Figures 2~5 comprises a cylindrical body 5 formed of
7 electrically insulating material. The body 5 has a bore 6
81 closed at one end by a wall 7 provided with a pair of
9 diametrically opposed openings 8 therein which communicate
10 with the bore 6. The opposite end of the bore 6 is open.
11 Adjacent the closed end of the bore the latter is provided
12¦ with a pair of longitudinally extending diametrically opposed
13¦ ribs 9 each of which has a groove 10 therein.
'` 141
Fitted into the bore 6 and seated against the end
16¦ wall 7 is an elongate sleeve 11 having a cylindrical bore 12
17 ¦ extending therethrough. The sleeve 11 is longer than the body
18 5 and that part of the sleeve which extends into the bore 6
19¦ has diametrically opposed, radially projecting ribs 13 that
are fitted into the grooves 10 to preclude rotation of the
21 sleeve 11 relative to the body 5.
221
23 Accommodated in the bore 12 and seated at one end
241 against the end wall 7 is a biasing spring 14 having a prede-
2B¦ termined capacity. Also accommodated in the bore 12 is a
26¦ biasing mass 15 having a predetermined weight and comprising
27 ¦ a preferably metallic body 16 that is both slidably and ro-
28¦ tatably received in the bore 12. The body 16 terminates at
2~ one end in a reduced diameter extension 17 fitted into the
~ol spring 14 and which forms a shoulder 18 against which the
- 6 -
:
1 ¦spring 14 seats. The opposite end of the body 16 also
2 ¦terminates in an e].ongate, reduced diameter extension l9
3 ¦fitted at its free end with an electrically insulative cap 20.
4 l
That end of the sleeve 11 which projects beyond
61 the body 5 terminates in an annular outer skirt 22. Adjacent
r ¦ the skirt is a reduced diameter, annular neck 23 that is
8 accommodated in the bore 6. The skirt 22 is threaded to
9 accommodate a correspondingly threaded plug 24 having an
annular groove 25 therein in which is fitted a preferably
ll glass cylinder 26 form.ing a tubular bore or passage 27 having
12¦ a smooth surface. The cylinder 26 extends inwardly of the
13¦ sleeve ll and beyond the plug a distance sufficient to be
l4 received in and supported by the neck 23.
16 Accommodated in the bore 27 of the cylinder 26
17 is a preferably spherical sensing mass 29 formed of an
18 electrically conductive, low expansion metal. The mass 29
l9 normally seats on a semi-spherical surface 30 formed at the
inner end of the plug 24. A spherical mass is preferred to
21 a cylindrical mass, for example, because a spherical mass
22 can roll and thus is much less susceptible to friction forces,
and also because a cylindrical mass can cock causing major
changes in fluid flow resistance. Both of these effects
give rise to erratic behavior.
26
27 In the embodiment shown in Figure 2, the diameters
28 of the bore 27 and of the mass 29 are chosen to establish a
clearance 31 bet.ween them of such size as to provide for
inertial flow of fluid (air or other gas) through the
::
- 7 -
1 clearance for the purposes of damping movement of the mass
21 relative to the cylinder. Such inertial fluid flow results in
3 a sensor having a high velocity chanye for short duration
41 pulses and thus provides additional protection against in-
51 advertent actuation of a passenger restraining device due to
6¦ short lived pulses caused by breakaway poles or hammer blows,
7 for example.
81
I Between its ends the sleeve 11 is provided with
a pair of diametrically opposed slots 35 for the accommodation
of electrically conductive switch blades 36 having bowed
12¦ contact portions 37 spaced apart from and confronting one
13 another and forming normally open contacts. The blades 36
14 ¦ have corresponding free ends 38 at one end of the slots 35
15¦ which rest upon the neck 23 of the sleeve 11. Encircling the
16¦ ends 38 of the contact blaaes is an elastic band 39 which
17 ¦ yieldably maintains the ends of the conductive blades against
18 the neck. Adjacent the opposite end of the slots 35 the
19¦ conductive blades extend through the grooves 10 and end in
20 ¦ terminals 40 which project through the opening ~. One of the
21¦ terminals 40 is adapted for connection by a conductor 41 to
22 ground through an energy source such as a battery 42, and
23 the other terminal 40 is adapted for connection by a conductor
241 43 to an operator 44 of known construction that is operable to
activate a passenger restraining instrumentality 45 such as an
26¦ inflatable airbag. The terminals 40 are flexible and may be
27 ¦ bent from the positions shown in Figure 2 so as to extend
28¦ through the bushing 3 and be connected to the conductors 41
2~ and 43 which are within the cable 4. .
~ol
':', ' , : .
.
1 ¦ ~t least one side of the sleeve 11 is provided
2 ¦wi~h a flattened surface ~6 that is substantially tangential
3 ¦to the inner surface of the bore 12. Fixed to the flattened
¦surface 46 is a plate 47 in which is formed a slot 48. The
5 ¦slot has a linear portion 49 which extends longitudinally of
6 ¦the bore 12 and communicates with a plurality of sinuous or
71 zig-zag slot portions 50,51, and 52. In the disclosed embodi-
81 ment, the slot portion 50 extends at an angle of about 45
9 from the slot portion 49, the portion 51 extends at an angle
of about 90 to the portion 50, and the slot portion 52
11 extends at an angle of about 90 to the slot portion 51. The
12¦ angularity of the slot portions may be different from that
13 specified.
14
15¦ The sleeve 11 is provided with an elongate, linear
16 slot 53 of greater width than that of the slot 49 and extend-
17¦ ing parallel to the longitudinal axis of the bore 12. The
18¦ slot 53 communicates with the bore 12.
191
20¦ Fixed to the biasing mass 16 and projecting
21 laterally therefrom through the slot 53 and into the slot 49
22¦ is a pin 54. The pin 54 is slidable longitudinally of the
23 slot 49 and is capable of following the sinuous path formed by
: 241 the slot portions 48-52. Since the body 16 is rotatable as
25¦ well as linearly movable wi-thin the bore 12, movement of the
26¦ pin 55 longitudinally of the slot 49 will cause the body to
27 ¦ be oscillated according to the path defined by the slot 49.
28¦ The slot 49 and the pin 54 constitute means for damping
20¦ movements of the biasing mass 16.
~501
1 The embodiment of the invention shown in Figure 6
21 is the same as that described earlier, except for the
3 differences noted below.
41
The plug 24a (corresponding -to the plug 24) has
6 a bore 56 in communication with a sharp edged orifice 57,
7 thereby forming an air passageway through the plug 24a. The
diameters of the bore 27 and the mass 29 are virtually the
9 same, thereby limiting -the clearance 31a between the bore 27
and the mass 29 to an amount just sufficient to enable movement
11 of the mass within the bore and to minimize fluid flow between
12 bore 27 and the mass 29. To minimize the possibility of the
13¦ entry of foreign matter into the orifice 57, an air permeable
14 ¦ membrane 58 is adhered to and covers the open end of the
151 skirt 22.
16
17¦ To condition either of the two embodiments of
18¦ sensors disclosed herein for operation, it is fitted into
19¦ the cavity of the casing 1 and the terminals 40 connected to
20 ¦ the conductors 41 and 43. The cavity within the casing 1 is
21 of such size as to maintain the body 5 and the sleeve 11 in
22¦ assembled relation. The casing then may be bolted or otherwise
secured to some portion of a vehicle with the longitudinal axis
24¦ of the sleeve 11 substantially parallel to the longitudinal
251 axis of the vehicle. If the casing is mounted at some frontal
26¦ portion of the vehicle, such as the bumperr a fender, or the
27 ¦ radiator the characteristics of the sensor will be different
28¦ from one that is mounted on the vehicle's firewall, as will
2 ~ be explained.
:'
I - 10 -
1¦ ~ sensor corresponding to -tha-t disclose~ in Figure
2 2 is adapted to be mounted on the Eirewall of a vehicle
31 traveling in the direction of the arrow 60 (Figure 2).
4 ¦Deceleration of the vehicle, if suEficiently abrupt, will
subject the bias mass 16 and the sensing mass 29 to an
61 acceleration pulse in the direction of the arrow 60. If
7 the acceleration pulse is sufficient to overcome the force
8 of the spring 14 the bias mass 16 will move in the direction
9 of the arrow 60, thereby disengaging the sensing mass 29 so
as to enable the latter also to move in the direction of the
llj arrow 60. The capacity of the spring should be such that an
12¦ acceleration pulse must exceed a predetermined threshold, such
13 as 3 Gs, before the bias mass 16 is capable of moving relative
14¦ to the sleeve 11. However, the capacity of the particular
spring 14 selected may be varied to achieve optimum results.
161
1~ 1 If the acceleration pulse is of such magnitude as
18¦ to enable the bias mass 16 to overcome the force of the spring
19¦ 14, and is of sufficient duration, linear movement of the
20 ¦ bias mass can be quite rapid, and could be sufficiently rapid
21¦ to cause the mass to bottom on the wall 7 and rebound. In
221 the present construction, however, unrestricted linear movement
23 of the bias mass 16 may continue only until such time as the
241 pin 54 reaches the angular slot portion 50, whereupon the mass
25 1 16 is forced to rotate in one direction as it continues to move
26¦ toward the wall 7. As the pin 54 approaches the slot portion
27 ¦ 51, such rotation of the mass 16 terminates and it is rotated
2~ ¦ in the opposite direction. In this manner the kinetic energy
2~ ¦ of the bias mass 16 is partially dissipated and movement of
~0 ¦ the mass is damped. It is possible that the bias mass 16 may
~ '7~
1 ¦be subjected to an acceleration pulse of such magnitude and
2 ¦duration that the mass will bottom on the wall 7 and
3 rebound notwi-thstanding damping of its movemen-t. In this
4 event, rebounding movement of the mass also is damped by the
cooperation of the pin 54 and the slot 48.
61
71 When the bias mass 16 is subjected to an
81 acceleration pulse sufficient to effect disengagement of the
9 latter from the sensing mass 29, the latter mass, being sub~
jected to the same acceleration pulse, is enabled to move in
11 the same direction as the bias mass 16. After sligh-t movement
12 of the sensing mass ~9 off its seat 24, a partial vacuum is
13¦ formed between the mass and the seat. A pressure differential
1~¦ thus is created across the sensing mass and produces a damping
force which opposes further movement of the mass. Gradually,
161 however, fluid will leak past the mass 29 at a rate that is
17 determined by the size of the clearance 31. Preferably, the
18 clearance is of such size as to provide for inertial flow
19 of the fluid through the clearance 31, rather than viscous
flow, and to provide the desired rate of longitudinal movement
21 of the sensing mass as explained in the aforementioned patent.
22
23 If the acceleration pulse is of sufficient
24 magnitude and duration, the mass 29 eventually will move to
a position in which it bridges the contacts 37. The diameter
26 of the mass 29 is greater than the spacing between the contacts
27 37 thereby assuring good contact between the blades and the
28 mass 29 to effect closing of the switch thus formed by the
2~ blades and mass to actuate the mechanism 44 and inflate the
~0 airbag 45. To ensure against bouncing or rebounding of the
1¦ blades 37 as they are engaged by the mass 29, the elastic
2¦ band 39 imposes a yiel~able force on the blades to restrain
3 their separa-tion and maintain them in firm engagement with the
41 mass 29.
61 In the construction illustrated in Figure 2, the
7 length of the linear slot portion 49 is such that, by the
8 time the mass 16 has moved a distance to enable the pin 54
9¦ to enter the slot portion 50, the bias mass also has moved a
distance sufficient to enable the sensing mass 29 to engage
11 and bridge the contacts 37. This is the arrangement preferred
12 when the sensor is mounted on a vehicle's firewall.
131
14 If the sensor is to be mounted on an energy
absorbing portion of a vehicle, such as the front bumper or
16¦ fender, a slightly different relationship between the bias
17 ¦ mass 16 and its damping means is preferred so as to delay
18¦ initiation of the inflation of the airbag. This effect may
19¦ be achieved by shortening the length of the linear slot portion
20¦ 49, i.e., locating the first angular slot portion 50 closer
21¦ to the initial position of the sensing mass 29. In such an
22¦ arrangement damping of the movement of the bias mass 16
23 commences prior to the time that it is moved a distance
24¦ sufficient to permit engagement of the mass 29 with the
251 contacts 37. In such a construction the acceleration pulse
28¦ not only must exceed the force of the spring 14, but also
27 ¦ must be of sufficient duration to enable movement of the
2B¦ bias mass 16 a distance great enough to permit movement of
2~1 the sensing mass 29 into engagement with the contacts 37.
~ol This arrangement makes it possible to distinguish be-tweQn
~: . ~ . , .: ,
l ¦crashes necessitating deployment of the protective device and
2 other, shor-t dura-tion pulses.
4 The operation of the sensor embodiment illustrated
in Figure 6 is quite similar to that of the previously des-
61 cribed embodiment with the exceptLon that, in the modified
7 embodiment, movement of the sensing mass 29 is damped by
8 restricting the flow of fluid to the space between the mass
9 and the seat 30a by means of the sharp edge~ orifice 57. In
the modified construction the clearance 31a between the mass
11 29 and the bore 27 is less than the clearance 31, and should
12 be just sufficient to enable movement of the mass 29 relative
13¦ to the cylinder 26, thereby assuring that the dominant damping
14¦ influence on the mass 29 is attributable to the fluid. The
15¦ flow characteristics of the fluid through the orifice ,
16¦ preferably are inertial.
171
18¦ The ability to damp not only the movement of the
19 sensing mass 29, but also the bias mass 16, coupled with the
20 ¦ latter's ability to enable or disable free movement of the
21¦ sensing mass 29 into agreement with switch contacts, permits
22 sensors having greatly di~fering operating characteristics to
23 be produced. Thus, sensors constructed in accordance with the
~4 ¦ invention are capable of operation regardless of whether they
251 are mounted at frontal or rearward positions on a vehicle and
26¦ are effective to sense the need for operation of a passenger
27 ¦ protective device and initiate operation of such device in
28¦ sufficient time to provide protection for a vehicle occupant.
2~1
The disclosed embodiments are representative of
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l ¦presently preferred forms of the invention, but are intended
2 ¦to be illustra-tive ra-ther than definitive. The invention is
1 deiined i the claims.
D
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261
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