Note: Descriptions are shown in the official language in which they were submitted.
~4~8~
This invention relates to an acceleration sensing
device for sensing acceleration above a certain magnitude,
and more particularly to an acceleration sensing device
to be installed in an automobile for sensing large
accelerations which may be applied upon a rear-end or
head-on collision and activating a safety means for the
passengers, and to one to be installed in an industrial
machine for sensing earthquakes of magnitudes above a
... .
certain value and activating a safety means for turning
off power sources, fuel sources, e-tc. to prevent electri-
cal shocks, fires, explosions, etc.
A conventional acceleration sensing device used in
airplanes, etc. comprises three components; a weight,
a resilient memberl.for supporting this weight, and a
housing. The devicel~d~tects the accleration by the displace-
ment o~ said weight. :[n thecase of detecting an impact
acceleration in ~uch a structure, it talces some length
of time for ~he wei~ht to achieve a certain displacement.
This time lag is a large drawback in the case of aontrol- ~
ling another machine by the detection of acceleration. ; ;
Further, the restricing force of the resilient member
for the weight may vary one by one due to the varia-tions
in treatment, internal strainl , time-dependent deterior- `
ations of mechanical properties, etc. and increase the
detection error. Further, said conventional acceleration ,
sensing device has a drawback that acceleration only in
a particulàr direction can be detected.
This invention is intended to eliminate said conven- -
, .~. .
tional drawbacks.
An objec-t of this invention is to provide an
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acceleration sensing device capable of detecting acceleration
. in any direction. When one unit can detect acceleration in any
direction, the electrical circuits and the structure of the
safety means can be simplified to a large extent.
nother object of this invention is to provide an
acceleration sensing device having a rapid response speed, i.e.
i the time length from the application of an acceleration to -the
activation of a safety device.
A further object of this invention is to~provide an
acceleration sensing device having a simple and compact structure.
.
- According to the present invention there is provided
an acceleration sensiny device comprising an electrically con-
ductive horizontally disposed cylindrical non-magnetic support
riny having a hole of predetermined radius, an insulating
1 substrate supporting said support ring, an electrical:Ly conductive
Y sphere hav~ng a radius larger than that of the hole o~ said
support ring and placed on the upper inner periphery of said
support ring, an electrically conductive contact member, means -
~; supporting said contact member fixedly above said sphere and
J 20 spaced therefrom when the sphere is normally on the support ring,
said contact member having an axis substantially coaxial with the
; axis of the hole in said suppor-t ring, and an inverted support
member having a depending por-tion tightly fixed to said insulating
substrate, said support member covering said support ring and
said sphere and having said contact member adjustable mounted ;
thereon for setting the gap between said contact member and said
. .
sphere, thereby establishing an electrical path between said
support ring and said contact member when an acceleration having
- a hori~ontal component greater than a predetermined value is
~pplied to the sphere causing it to pivot on the inner edge of
said suppo~t ring to make contact with the contact member.
According to the present invention as described above,
,
1 2
. . ;., .
- the following effects can be provided:
(1) An acceleration in an arbitrary direction of the
three dimensional space including the horizontal and vertical
directions (not only a predetermined direction) can be detec-ted.
(2) The response speed is rapid.
(3) The structure becomes simple and compact.
Other objects, features and advantages of the present
. invention will become apparent from the detailed description
~- when taken in conjunction with the accompanying drawings in whieh:
Figs. 1 and 2 are cross-sections of conventional
aeeeleration sensing devices, respect1vely;
Fig. 3 is a cross-section of an embodiment o~ an
aeeeleration sensing deviee;
; Fig. 4 is a cross-section oE the deviee of Fig. 3 but ~'
applied with an acceleration;
Figs. 5, 6 and 7 are cross-sections of other embodiments ~
aeeording to this invention; ~ -
Figs. 8 and 9 are perspeetive views of the ease and
' :~
~ the support ring of the deviee of Fig. 7;
,~ 20 Fig. 10 is a eross-section of ano-ther embodiment of
an aeeeleration sensing devlee;
Fig. 11 is a part:ial bottom view of the device of
Fig. 7 or Fig. 10; ~ ;
Figs. 12, 13, 14 and 15 are cross-sections of other ;
embodiments of an acceleration sensing device;
Fig. 16 is a eross-section of the device of Fig. 15 ;
:
. along the line XVI - XVI; '
Fig. 17 shows an output signal waveform of the device
of Fig. 15;
' 30 Fig. 18 is a cross-seetion of another embodiment of --
the aeceleration sensing device; ~-~
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Fig. 19 is a cross-section of the device of Fig. 18
~ along the line XIX - XIX;
-¦ Figs. 20, 21 and 22 are cross-sec-tions of other
embodiments of an acceleration sensing device;
Fig. 23 is a cross-section of the device of Fig. 22
along the line XXIII - XXIII;
Fig. 24 is a cross-section of a modification of the
device of Fig. 22;
' Fig. 25 is a cross-section of another embodiment of
. 10 an acceleration sensing device;
. ~ Fig. 26 is a perspective view of the support: ring for
the device of Fig. 25;
, Figs. 27, 28 and 29 are perspective view oE other
.
embodiments of the support ring shown in Fig. 26;
:
Fig. 30 is a cross-section of the ring of Fig. 29
along the line XXX - XXX;
Fig. 31 is a perspective view of another embodiment of
an acceleration sensing device;
:l Fig. 32 is a longitudinal cross-section of -the device
ll 20 o Fig. 31 along the line XXXII - XXXII;
Fig. 33 is a perspective view of the device oE Fig. 31
seen from the bottom;
~; Figs. 34, 35, 36 and 38 are cross-sections of other
embodiments of an acceleration sensing device;
Fig. 37 is partially cut-away perspective view
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of the device of Fig. 36;
Fig. 39 is a partial cross-section of a modification
of the device of Fig. 38;
Figs. 40a to 40e are perspective views of examples
of the insulating subs-trate for an acceleration sensing device;
Fig. 41 is a schematic diagram of a safety belt
locking system for an automobile using an acceleration sensing
device;
"~ Fig. 42 is an electric circuit diagram of the system
-~l 10 of Fig. 41;
Figs. 43a and 43b show signal waveforms for illustrat- ~
ing the operation of the electric circuit of Fig. 42; and ~ ;
, , 1:,
Figs. 44 and ~5 to ~6 are perspective Vi~W.5 oE other
, embodiments of the support ring assembly for an acceleration
sensing device.
Before the description of the embodiments of this
invention, typical examples of the conventional acceleration
sPnsing device will be described briefly referring to Figs. 1
and 2.
', 20 Figs. l and 2 show basic conventional struc-tures of
acceleration sensing devices both of which comprise a weight l,
a resilient member 2 for supporting this weight 1, and a housing
3 for containing those elements and detecting the magnitude of
. ', . ' .':
; displacement of said weight 1 caused by the force applied to
said weight 1 to detect acceleration. Various drawbac~s as
described before accompany the use of the resilient member.
Hereinbelow, the embodiments of the present
-
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invention will be described referring to the drawings.
Fig. 3shows an acceleration sensingdevice whichcomprises a
housing 13 formed of an insulating material, an electrically con-
ducti~e support ring 15 fi~ed on the bottom of said housing 13,
an electrically conductive sphere 14 placed on the upper inner
periphery of this support ring, and an electrically conductive
contact member 16 covering the aperture of the housing 13. The
contact member 16 is screwed into the threads formed in the inner
surface of said housing 13. Fig. 3 shows the state under no ac-
celeration. In this case, the conductive sphere 14 and the con-
tact member 16 do not contact each other and hence the support
, . .
ring 15 and the contact member 16 are electrically cut off.
When an acceleration a as written by the formula
a > y-r/ / R2 _ r2 ~ ;
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is applied to the sphere, where R and r are the radii of the sphere
14 and the aperture of the support ring 15 and g is the gravita-
tional acceleration, the sphere 14 moves about a point on the upper
inner periphery of the support ring 15 and contacts the contact
member 16 as is shown in Fig. 4. This contact between the sphere
14 and the contact member 16 can be detected as an electrical con-
duction between the support ring 15 and the contact member 16 for
- use as an acceleration detection. In this acceleration detection,
the least magnitude of acceleration to be detected can be set by
selecting the radius of the aperture of the support ring 15. Fur- ~ ;
ther, the
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response speed can be easily selec-ted by adjusting the ~ap between
the contact member 16 and the sphere 14 through the adjustment of
the contact member 16. If an acceleration is an impact in a short
tirne period, the sphere 14 contacts the contact member 16 in a
collision, repea-ts several bounces and then rests still. In this
case, it is necessary to detect the ~irst collision between the
contact member 16 and the sphere 14 as the electrical conduction ,,, `
between the member 16 and the support ring 15 to detect the accel- ~
eration.
When the response speed is of less importance, those de- ~ ;
vices as shown in Figs. 5 and 6 which detect acceleration through '
the contact between a sphere 14 and the inner wall of an electri-
cally conductive housing 13 are also effective. The devices shown
in Figs. 5 and 6 are provided wi-th insulative substrates 17.
Figs. 7 to 9 show another embodiment of the acceleration
sensing device. In the figures, a conductive support ring 20,has
a through hole 21 and is provided with unitary terminals 22 on the -~
lower surface. The terminals 22 are inserted into the holes 24 in
a printed board 23 and soldered with conductive pattern 25 formed " '~
of the lower surface of the printed board 23. A conductive sphere
26 has a diameter larger than -that of the aperture 21 of said sup-
port ring 20 and is placed on the upper inner periphery of the hole
. .. .: .
21 of said support ring 20. A conductive casing 27 has a bell ,
shape as shown in the figure and an open end provided with unitary
terminals 28. These terminals 28 are inserted into respective holes ,'
29 in the printed board 23 and soldered with a conductive pattern 30 ~ "
provided on the lower surface of the '
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1 printed board 23 as is shown in ~ig, 7. A conductive
corltact member 31 is screwed into the upper part of said
casing 27 and supported thereat. The lower surface of this
; contact member 31 is disposed above said sphere 26 with
a predetermined gap therebetween. Said contact member 31
:
is fixed to the casing 27 with a locking nut 32.
Electronic parts 33 are connected to and mounted on said
.:
printed board 23.
When an acceleration expressed by
;:
a ~ g-r/ ~ _ r2
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, where, g is the grav:ltational accelera-tion, and R ancl r
are respective radii of the sphere 26 and -the aper-ture 21
of the support ring 20, is applied in a horizontal direc-
, tion the sphere 26 moves about a point on the upper inner
~, 15 periphery of the support ring 20, contacts the con-tact ~ -
member 31 and allows the electrical conduc-tion between
the conductive support ring 20 and the conductive casing
27 therethrough, The contac-t between the sphere 26 and
the contact member 31 can be electrically detec-ted as a
voltage drop of the voltage applied between the support
; ring 20 and the contact member 31, Here, if the accelera- ;
tion applied to the device is an impact, the sphere 26
repeats several bounces against the contact member 31.
In this case, the first contact should be detected in the
acceleration detection.
~igs. 10 and 11 show another embodiment of the
~, . . .
acceleration sensing device. In this embodiment, screw
threads 35 are formed in the open end por-tion o:E a housing
1 34 and similar screw threads 36 are formed in a support
ring 20. The support ring 20 and the housing 34 are fixed : :
on a printed board 23 by screws 37 and 38 using said
- threads 35 and 36. In this case, the electrical conduc-
:..
5 tion between conductive patterns 30 formed on the printed ..
board 23~ ~e support ring 20 and the housing 34 is
obtained through the screws 38 and 37, respectively. :~
Fig, 11 shows the lower surface of the printed board ,.
23 of the embodiment shown in Fig. 10. .; .~
According to the above embodiments, there can ` ~.
. ::. .
be provided the following effects: :
An acceleration in any horizontal direction can .~ .
be detected;
. ~ .
The structure is simple and hence can be made
15 compact; and . :~:
, The structure can be easily assembled by screws ;~ .
or soldering terminals on a printed board and the . ,
, electrical conduction with a conductive pattern can be
provided simultaneously with the assembly.
Fig, 44 shows an example of the support ring -; :.
Eor the pre~ent acceleration sensi.ng device, A conduc-
tive plate ls punched to :Eorm a hole 211 and projec-tions
212, These projections 212 are bent downward, Thus a
support ring 213 can be formed simply, In attaching this ~:.`
25 support ring 213 to an insulating substrate 214 shown in ~.
Fig, 45, the projections 212 of the support ring 213 . `
are inserted into holes formed in the insulating substrate
214 and then bent on the lower surface of the substrate `;
214 to fix it. In the case of punching the support ring ~. ` `
` 30 213 by a press machine, a ring body 215 having a step
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portion as shown in Fig. 46 may be formed separately. In this
case, the ring body 215 is fixed on the substrate 214 by the sup-
~: port ring 213 shown in Fig. 44. A sphere is placed on the upper
inner periphery of the hole 216 of the ring body 215.
Fig. 41 shows schematically a safety belt locking sys-
tem for an automobile using the present acceleration sensing de-
vice. The system comprises an acceleration sensing device 200 A, by
~ay of example as shown in Fig. 13 a drive circuit 200 B, and a
safety belt locking system 200 C. First, the sa~ety belt locking
system 200 C will be described.
In the figure, an automatic reel drum 201 is rotatively
supported between side plates 202 and 202'. A ratchet wheel 203
i5 fixed to thLs reel drum. A seat belt 204 is coiled on said P
reel drum 201 and usually subjectéd to a winding force about the :
drum 201 by a re~ilient member provided in said automatic reel
drum 201. This seat belt 20g is provided to restrain a passenger
of an automobile, but is usually freely pulled out and in. A
pawl 205 is rotatively supported between said side plates 202 and
... . . .
-~ 202'. A solenoid 206 is provided to drive said ratchet pawl 205.
~ . ... .
~20 Fig. 42 shows the electric circuit for said safety belt
locking system, which includes a monostable multivibrator 200 D ,~
constituting the driving clrcuit 200 B of Fig. 41, a switching
transistor Tr3, and a battery E. The operation of said safety belt
locking system wlll be described.
When a passenger sits on a seat in an automobile and
winda a safety belt around his body, a sphere 43 in r
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said acceleration sensing device rests still on a support ring 40
if the automobile is at a standstill or is run at a constant speed.
In such a case, the sphere 43 and the contact member ~5 are elect-
rically cut off. Thus, transistors Trl and Tr2 constituting the
monostable multi-vibrator 200 D and the transistor Tr3 are kept
"off", "on" and "off" respectively and hence no current is allowed
to flow through the solenoid 206. Therefore, the ratchet pawl 205
; and the ratchet 203 of the reel drum 201 do not engage with each
other. Therefore, the seat belt is freely drawn or pulled back and
the passenger does not feel a restraining force Erom the safety
belt 204.
If the automobile is applied with an emergency brake or
collides with something and is applied with an impact acceleration, ;
the sphere 43 moves on the support rin~ 40 as is shown by the dotted
line in Fig. 41. Then, -the sphere 43 contacts tlle contac-t member
45 several times, and the contact member 45 and -the support ring 40
are interMittently driven into conductive state through the sphere - --
,:
43 as is-shown in Fig. 43a. Hence, the monostable multivibrator
200 D is reversed for a period determined by the capacitance Cl and
the resistance R and the transistors Trl Tr2 and Tr3 are turned
"on", "off" and "on" respectively. Thus, a current ls allowed to
~low through the solenoid 206 as is shown in Fig. 43b. Thereby,
the ratchet pawl 205 is driven by the solenoid 206 to engage with
the ratchet 203. Therefore, the safety belt 204 is locked and pre-
vented from being drawn out and hence restrains the passenger to
the seat. r
Figs, 31 and 32 show another embodiment of the -
.
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~; 1 acceleration sensing device, in which a conduc-tive support
ring 111 having a hole 116 is fixed on an insulating
substrate 113 and a conductive sphere 112 is set on the
upper inner periphery of the aperture 116 A U-shaped .
:~- 5 conductive plate 122 is formed by bending a metal plate
. and provided with unitary projections 117. These projec- :
tions 117 are inserted into the holes 118 formed in said
insulating substrate 113 and then bent on the lower surface
of the insulating substrate 113 to fix the conductive
plate 122 to the insulating substrate 113 as is shown in
Fig 33. A contact member 114 is supported by said con-
ductive pl.at0 122 and fixed by a locki~g nut 115 to prevent
the relatlve motion of the contact me~lber 114 due to
vibrations, etc .
Fig. 34 shows another embodiment in which an
elongated contact ribbon 138 having a resilience is
warped in a circle-like shape and has the both ends fixed
to a support ring 132. A sphere 134a is put in this circle -;
so that the top of this sphere contact the central portion
of -the contact ribbon 138 Namely, in the absence of the
~ sphere, the height of the contact ribbon 138 is arranged
:. smaller than that of the sphere 134a. Thus, when the
~ as~s
sphere 134a 1s inserted, the contact ribbon 138 ~e~
. the sphere 134a downward with a minute force by the
25 resilience of the contact ribbon 138. The contact ribbon :~
138 and the sphere 134a are -thereby always driven to ::
mutual contact. If the top of the sphere 134a is displaced . . .
. in any movement of the.sphere 134a, the contact ribbon. .~ .
~ 138 is also displaced upward or downward. Thereforej if
.~ 30 the sphere 134a is moved by an acceleration a, the contact ~ .
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1 ribbon 138 ls lifted upward to contact the contact member
136. The contact ribbon 138 moves vertically in parallel
sense and hence -the contact portion with the contact member
- 136 becomes a line or plane, theoretically. Thus, the
contact area increases extremely. In this structure,
since the contact ribbon 138 is directly connected with
the support ring 132 and the electrical conduction is ~
achleved through the support ring 132, the contac-t ribbon -
138 and the contact member 136, the sphere 134a may not ~
: : .
be conductive.
, - : ,-.
Fig 35 shows another embodiment in which a ;
conductive plate 139 is fi~ed at one end to enhance the
; movement of a sphere 134a. In the structure of Fig 34, ;-
the force constant of the contact plate 138 may become
fairly large from its structure and apply, an excess
force to the sphere 134a to increase variations of the
detected accelerations whereas in the structure of ~ig
35, the contact plate 139 is supported only at one end
~ .
, and hence can have a small force constant to considerably
depress variations of the detected acceleration~.
~; Figs. 36 and 37 show another embodiment in
which a plurality of guide pins 140 is provided to a
support ring 132a and a contac-t plate 141 is provided ~ ;
movable along the guide pins 140 in the vertical direction
~5 and is applied with a downward force by coil springs 142.
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Insulating b~hcs 1 ~ are formed on the frame 135 for
supporting -the upper end of said guide pins 140. Electri-
cally, a current may be allowed to flow from the support
ring 132a through the guide pins 140 to the contact
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~; 30 plate 141, or from the support ring 132a through the
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sphere 134b to the contact plate 141. In the former case, the
sphere 134b may not be conductive as in the cases of Figs. 34 and
35, but it should be conductive in the latter case. Further, the
sphere 134b and the contact plate 141 contact each other in a point
contact. But since they are always contacted, there is little pos-
- sibility of poor conduction.
~ Fig. 38 shows another embodiment in which a contact plate
; 144 provided on a conductive sphere 134 is pressed downward by a
coiled spring 145. An insulating bu~hing 146 is provided at the
seat of the spring145 to achieve insulation from the contact 136
and the frame 135. According to this embodiment the diameter of
the coiled spring 145 can be selected large and hence the force
constant can be selected very small to decrease the depressing
force for the sphere 134 and thereby to minimize the variation of
th~ detected acceleration.
Fig. 39 shows another embodiment in which a roller 147
is depressed downward by a coiled spring 150 and a seat 149 and
partially projects from the aperture of a housing 148 ta contact a
contact plate 144. The open end of the housing 148 is arranged by
tapering the topportion etc.not todrop theroller 147: The roller147 is
bearing on an axis 151 around which the roller is rotàtable. The
axis 151 is vertically slidably mounted against the spring 150 in ;
the housing. The housing 148 is pressed into a screw 136a. Said ;
roller 147, coiled spring 150, housing 148 and screw 136a shou~d be
: .
l conductive. By the contact of the contact plate 144 with the rol-
-, ler 147, the roller 147 rotates and a new contact por~ion appears
successively. If the contact plate 144 moves purely vertically,
the roller 147 does not rotate. If, however, the direction of the
force of the coiled
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spring 150 is off-set from the center line of the roller 147, the
rotation of the roller 147 is relatively easily provided.
Fig. 12 shows another embodiment in which a conductive
support ring 42 having a hole 41 is fixed on the upper surface of
an insulating substrate 40. A conductive sphere 43 having a dia-
meter larger than that of the hole 41 of the support ring 42 is
placed on the upper inner periphery of said supporting ring 42. A
conductive housing 44 is fixed on said insulating substrate 40 and -
covers said sphere 43 and said support ring 42. ~ contact member
45 is screwed into and supported by the upper portion of the hous-
ing 44. A locking nut 46 fastens said contact member 45. A lead-
wire 47 is electrically connected with said support ring 42 and
another lead-wire 48 is electrically connected with said housing
44. The insulating substrate 40 is fixed to and in an outer casing
49 by screws 50. The outside of the housing 44 is molded with a
resin 51 which has a relatively high thermo-insulation power.
~hen an acceleration a expressed by
,~i a ~ g.r./ ~ ` ~ ;
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where, g is the gravitational acceleration and R and r are the res- :
pective radii of the sphere 43 and the hole 41 of the support ring
42, is applied in a horizon-tal clirection, the sphere 43 moves about
a point on the periphery of the hole 41 of the support ring 42 and ~
contacts the contact member 45. Then, the lead-wires 47 and 48 are ;`
taken out from the housing 49 through an insulative grommet 49' and r
are ` ~
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1 electrically connected to detect the acceleration. In
the above embodiment, it is necessary for decreasing the
response time to decrease the gap S between the sphere ~
and the contact member 45. When the gap S is made small,
however, upon a rapid change of the ambient temperature,
usually the housing 44 is first subjected to an expansion
-; or contraction and then the parts inside the housing 44
such as the sphere 43 is subjected to a similar change,
~ rrhus~ the gap S is subjected to a change which causes
- 10 a change in the response speed, In the embodiment shown
in Fi.g, 12, since a resin 51 of high thermal insulation
is disposed around the housing 44, changes of the response
speed of the total system due to temperature changes are
prevented and the acceleration can be rapidly and correctly
.:
sensed,
, Fig, 13 shows another embodiment, in which the ~
inside of a casing is evacuated -to enhance the thermal ~ :
insulation, An outer casing 53 is fitted to an insulating
substrate 40 through a seal 52 and a bottom cover 56
provided with terminals 54 and 55 is -fit-ted to the insulat-
; ing substrate 40 through another seal 57, r~he inside
of the outer casings 53 and 56 is evacuated to improve the
, thermal insulation,
- Here, the inside o-f the outer casing 5~ and 56 ~
25 may alternatively be filled with a gas o-f high thermal `
insulation.
Fig, 14 shows another embodiment in which an
acceleration ~ensing mechanism and acceleration sensing
~' circuit parts 59 are enclosed in a casing 58 and
unitarily molded in a resin 60,
, .
~ - 16 -
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According to the above embodiments, there can be pro- - ;
vided the follbwing advantages:
An acceleration in any horizontal direction can be ~ -
sensed;
The structure is simple, does not need manufacturing
precision and hence can be manufactured at a low cost;
The response time does not change even a~ainst a rapld
i temperature change and hence the acceleration can be sensed cor- ~
rectly;
The system can be used in a wide range of temperature;
A compact acceleration sensing device can be provided. ;
In the embodiment of Fig. 14, in molding the accelera-
~, . .
tion sensing device in the casing 58- with the resin 60 such as
epoxy or silicone resin, it may happen that internal stress appears
due to the thermal contraction in setting the resin 60 and the
insulating substrate 40 may be bent concave due to this stress.
It is effective for preventing this bending to form a supporting - ;
, rib 164, 165, 166, 167 or 168 as shown in Figs. 40a to 40e on
the lower surface of the insulating substrate 40.
Figs. 15 and 16 show another embodiment in which a con-
ductive ring 70 having a hole 71 is fixed to the open bottom end
o a housing 72. An insulating bushing 73 and insula-ting ring 78
are fitted and fixed to the hole 71 of said support ring 70. A
conductive contact rod 74 is fixed to this insulating bushing 73.
~i . , .
This contact rod 74 is disposed at the center line of said support
ring in a manner that
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- l the top thereof is located lower than the upper end sur-
`~ Pace of said support ring 70. A conductive sphere 75 is
mounted on the upper inner periphery of said support ring
and contacts the top of said contact rod 74 when it is
` 5 at rest. ~ead-out wires 76 and 77 are connected to said ;~
contact rod 74 and said support ring 70, respectively.
Thus, an electrical circuit is formed through the lead
wire 76, the contact rod 74, the conductive sphere 75,
s the support ring 70 and the lead wire 77 when the sphere
lO is at rest. When an acceleration a expressed by -
a > g-r/ ~R2 _ r2
where, g is the gravitational acceleration and R and r
are the radii of the sphere 75 and the hole 71 of the
support ring 70 respectively, is applied in a horizontal `~ ;-
i 15 direction, the sphere begins to move in the direction of
the acceleration and departs from the contact rod 74 to
open the electrical circuit.
` When an acceleration as described above is `
applied to the system, the sphere 75 is allowed to separate
20 from the contact rod 74 momentarily. IP the accelera- ;
tion is an impact, however, the sphere 75 is held by the
~ inner wall of the housing ~, or returned by gravity which
`, brings back the sphere onto the support ring 70~ The ~ ;
sphere 75 repeats such an action and performs a damped
25 oscillation. The electrical conduction in such a damped
oscillation is as shown by the waveform of Fig. 17, . -
Referring to Fig. 17, if the first waveform
A is differentiated to de-tect the rising, the response
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speed can be depressed less than 1 msec. including the
retardation due to the electrical circuit. The least
acceleration to be detected can be selected at an
arbitrary value by selecting the relative value of the
radii of the sphere 75 and the hole 71 of the support
ring 70, R and r appearing in the above formula. In
the embodiment of Fig. 15, it can be achieved only by
altering the radius of sphere 75, to make it smaller or
greater and adjusting the position of the contact rod
74 by adjusting the screw.
'! , .,
The above embodiment provides the following advan- -~
tages:
An acceleration in any three dimensional direction
including the horizontal and vertical directions (not
only an accleration in a particular direction) can be
sensed;
~, The response speed is high;
The structure is simple and hence can be made complct; ~
Detection errors due to variations o-~ the resilient ~ ;
. . ,~ , .
member and the time-dependent mechanical deteriorations
can be minimized due to the elimination of any resilient
member such as a spring.
Figs. 18 and 19 show another embodiment, in which
a conductive support ring 80 having hole 81 `is supported
by an insulating bushing 82 at the lower end and sur~
rouned by a ring-shaped permanent magnet 84. The insul-
ating bushing 82 covers the open lower end of a housing
83. A conductive contact rod 85 is supported by the
l insulating bushing 82 at the central axis of the support
'~ ring 80. The top of the contac-t rod 85 is located
-- 1 9 -- , ~: .
,.', :
.,, ,j .
'~ ' ;, ~':
7',~
1 lower than the upper end of said support ring 80. A
conductive rigid sphere 86 is placed on the upper inner
periphery of said support ring 80. The sphere 86 contacts
the top of said contact rod 85 when it is at rest.
As is apparent, when the sphere 86 is at rest ~
~- on the support ring 80, the support ring 80 and the -
contact rod 85 are electrically connected through the
; sphere 86. The sphere 86 is attracted onto the support
ring 80 by the magnetic attraction from the magnet 84 as
: A lo well as by ~e gravity. When the sya-tem is subjected to
an acceleration a expressed by
a > (mg + F) . _ r
~IR2 ' r2 ,.
where, m is the mass of the sphere 86, g is the gravita-
tional acceleration, F is the magnetic attraction working
between the ,sphere 86 and the magnet 84, and R and r are
the radii of the sphere 86 and the hole 81 of the support
ring 80, the sphere 86 is allowed to depart from -the con-
taot rod 85 to cut off the electrical conduction be-tween the
, rod 85 and the ring 80.
According to thi~ embodiment in which the
sphere 86 is attracted not only by ~ gravity but also
by the permanent magnet 84, when the system is tilted,
errors of the acceleration detection are small compared
'~ to the conventlonal e~amples and the contact between the
'' 25 sphere 86 and the contact rod 85 is stable. ;~
Here, the least acceleration to be sensed can
~;~ be freely set by changing the radii of the sphere 86 and
the hole 81 of the support ring 80.
~.'.
.'' ~;'
~l - 20 -
: ``
1 Further, t;he detection of an acceleration is done
through the cut-of:E of the electrical conduction between
the contact rod 85 and the support ring 80. When an
. .
impact acceleration is appliedg the sphere 86 repeats
several bounces and then ~ on the support ring 80 due to
the repulsion from the housing 83, the gravity of the
sphere 86 itself, and the attraction from the permanent
magnet 84 Thus, the electrical conduction is interrupted
several times. It i9 necessary to detect the first cut-
`~ 10 off of the electrical conduction for sensing the accele-
ration.
Fig. 20 shows ano-ther embodiment, in wh:ich an
electromagnet 87 is used in place of the permanen-t magnet
84 of -the ~ystem o~ Flg. 18. In this embodiment, the
electromagnet core is made of a conductive material and
-,:
works also as the support ring r~his embodiment works
perfectly similarly to the foregriing embodiment.
Fig. 21 shows another embodiment, in which
the sphere 86 is depressed downward by a compression
.. . ..
spring 88 instead o:E the magnetic at-traction ln the -Eore-
going embodiments. This embodiment works also similarly
to the foregoing embodiments.
The above embodiments provide the following
.. ..
advantages:
An acceleration in any three dimensional direc-
tion including the horizontal and the vertical direction; ~ -
The response speed is high;
The s-tructure is simple and can be made com- `~
pact;
` ~0 Since the sphere is applied with a downward
,: ,'.', ' '~ '
, ., ;: :
.
..,
- 21
: ~ , .; . :
,
1 force by a permanent magnet, an electromagnet, or a
. ~ spring, errors ~ acceleration detection ~ small even :~
-` when the system is tilted;
The contact between the sphere and the contact
5 rod is stable. `
Figs. 22 and 23 show another embodiment. In .~; .
the figures, a conductive support ring 90 having a hole ..
91 is supported by an insulating bushing 92 which ~e~Ye~
~: the open lower end of a housing 93 and slidably supports
`
10 a conductive contact rod 94 in a hole 95 formed in the `:`
bushing 92. A spring 96 pushes up the con-tact rod 94 always :.
with a very small amoun-t of :Eorce. ~ conductive sphere 97
is placed on the upper inner periphery of` said support ring
90. When this sphere 97 rests still, it depresses said
: 15 contact rod 94 downward.
When the sphere 97 is at rest on the support
ring 90, the support ring 90 and the contact rod 94 are `
. electrically connected through the sphere 97. `
When an accelera-tion a satisfying the follow-
ing formula is appl:ied to the system in which the sphere
97 was at res-t, the sphere 97 is allowed -to depart from
the contact rod 94 -to cut off the electrical conduction ."
.
between the support ring 90 and the contact rod 94. ~` .
. :' ' ' `
~(ml + m2)g - kx} r .:~ :
: a > - ml ~ ~
25 Here, r and R are the radii of the hole 91 of the support .
ring 90 and the sphere 97 respectively, ml and ~2 are
the masses of the sphere 97 and the con-tact rod 94 res~
`I `., .
. pectively, kx is the force which the spring 96 generates :~
j .
. ~ :
..., ., ~ ; ' ,.
- 22 - .
'1 .. ' ` '
... . .. ~ . . . . , -,, . , ~
l upward when the sphere 97 is at rest, i.e. k is the force ~;
constant of the spring and x is the displacement of the
length of the spring, and g is the gravitational accele-
ration. -
In the elmbodiment as described above 9 the
contact rod 94 pushes up the sphere 97 with a minute force
:::
when the sphere 97 is at rest. Therefore, the contact
between the contact rod 94 and the sphere 97 becomes :
W~O~r~ , ,. "
stable. Further, the response time from the ~e~e~
when an acceleration is applied to the moment when the
electrical conduction between the support ring 90 and the
contact rod 94 is Cllt off can be easily and freely adjusted
by the stroke of the resiliency of the spring. Further,
the least value o-f -the acceleration -to be sensed can
be freely set by varying the radii of the sphere 97 and
the hole 91 of the support ring 90.
Fig. 24 shows another embodimen-t in which a
conductive spring 98 works also as the contact rod 94, ,~;
eliminating the use of the contact rod 94. This embodiment
provides similar effects as those of the foregoing embodi-
' ' '1
ment,
The above embodiments provides the followingadvantages:
:,
~ An acceleration ~ an~ three dimensional direc- -
~c~ .- :: :
1 25 tion including the horizontal and the vertical ~ a~L
: l .- -
can be sensed;
The response speed is high; s 1
' ~he structure is simple and can be made compact;
Since the sphere is pushed by a resilient ~;~
. 30 member such as a spring, the contact between the sphere
1, -
~ - 23 -
,'. '' .,' ;,~ .
. , .
1 and the contact rod or the spring becGmes stable. ~-;
~ig 25 shows another embodiment In the
s~ ~
figure, an insulating tr~shln~ 100 is fixed at the open
lower end of a housing 101. A ring-shaped support ring
102 is fixed on said bushing 100. The support ring 102 ~ ~:
is formed of two conductors 103 and 103' adhered through
an insulating plate 104 as is shown in Fig. 26. Here,
said support ring 102 is provided with a hole 106, the ;
upper inner periphery of which forms a circle A conduc- i~
10 tive rigid sphere 105 is placed on said support ring 102. ~ -
The diameter of said hole 10~ in the support ring 102
is smaller than that of the sphere 105.
When the sphere 105 rests still on the support
ring 102, the two conductors 103 and 103' forming the
support ring 102 are electrically connected through the
conductive sphere 105 When an acceleration a expressed
;~ by the following formula is applied in a horizon-tal direc-
~; tion, the sphere 105 is moved to separate from the support
ring 102 totally or except one portioh to cut off the
20 electrical conduction between the conductors 103 and `~
103'
; a ~ g.r/ ~R2 r2
Here, r and R are the radii of the hole 106 of the support
;l ring 102 and the sphere 105, and g is the gravita-tional
25 acceleration ~`
In the conventional acceleration sensing devices, '~t"~li'.~' l'
there exists some time lag from the application till
the detection of an acceleration, whereas in the present -
embodiment there exists no time lag if one ignores the
'`'''~ ~.','"',
. ".,, : '
1 ~ 24 -
.~ 1,: ,'.':
- \ :
7~
~ friction and the resistance of the air.
- Here, for preventing a difference in the least accel-
eration to be detected especially in the direction of
the insulating plate 10~ of the support ring 102, the
hole 106 should form a perfect circle and the upper sur-
face of the support ring 102 should form a perfec-t plane-
In manufacturing, however, it is often difficult to form
the same circle with two conductors 103 and 103' and
sandwiching an insulating plate 104 and to form the upper
surface in the same plane. If -the insulating plate 104
projects from the upper surfaces of the conductors 103
and 103', the sphere 105 contac-ts only one of the conduc-
tors 103 and 103' when it is at rest. In such a case,
it is apparent that the electrical conduction between
the conductors 103 and 103l cannot be obtained even when
no acceleration is applied. Thus, :i-t may be suggested
to shape the insulating plate 104 as is shown :in Fig 27,
in which the plate 104 is provided with a cut-away 107
or tapered so that the inner top of the insulating plate
, 104 is located lower than the upper surface of the
conductors 103 and 103'.
If the upper surface of the insulating plates 104
is lower than -the upper surface of the conductors 103
and 103' as is shown in Fig. 28, when an accelera-tion
is applied in the direction of the center line of the
insulating plates 104, the sphere 105 rides on the two
conductors 103 and 103' and the conduction is not cut
,- off. Thus, a cut-away 108 may be formed in each of the
two conduc-tors 103 and 103' at the portion neighboring
the insulating plates 104 as is shown in Figs. 29 and
30 so
,~ '" '
, 25 ~ ~
,:. ~ ':
,: ' ~
.
1 that the sphere moved from the s-table position in the
direction of the insulators 104 touch an insulator 104
and one of the conductors 103 and 103'.
When an acceleration above a set value is ~ -
. 5 applied to said system, the sphere 105 is allowed to
depart from the isupport ring 102 wholly or except for one
portion, collide with the housing 101, and repeat several
bounces I~ the acceleration is an impact, the sphere
105 will soon rest on the support ring 102. The accelera-
10 tion can be sensed by electrically detecting the first
cut-off of the electrical conduc-tion between the conductors
103 and 103'. Here, -the contac-t between the sphc:re and
~i -the conductors 103 and 103' is of very small pressure and .:; :
may be electrically unstable. Further, the inclination of
15 the housing greatly influences the sensed acceleration. . :
;f~ An improvement o~ the electrical property and a reduction
1 in the influence~ of the inclination o-f the housing can be
¦ provided by attracting the sphere downward by a sipring, a ~ :
¦ ` permanent magnet, or an electromagnet. . ~ :;
' i ' ' .' .' ,.
~ t~ ,'1 ' i!~
~ "". . '~.
'''1 '.'",'.';',"'.,
f : :
., . '``. ' .
: . - 26 - :,.
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