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Патент USA US3021464

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Feb. 13, 1962
R. A. PICKENS
3,021,454
CONTROL CIRCUIT FOR ELECTROMAGNETIC DEVICES
Filed April 11, 1958
L
l;
L “SOLENOID
e
m
I-FIG.‘
R8
R2
TX2
2
‘3
I,
c4
__
-:_- E
02
wiL
'
TX3
L
SOLENOID
R5
'
-
FIG. 5
"
ROBERT A. PICKENS
'
INVENTOR
BY
United States Patent O?ice
7
3,021,454
Patented Feb. 13, 1962
1
FIG. 2 is a schematic diagram of a‘ similar circuit in
which the'switch has been replaced by a power transistor
3,021,454
CONTROL CIRCUIT FOR ELECTRO
MAGNETIC DEVICES
Robert A. Pickens, Baltimore, Md., assignor to The
Bendix Corporation, a corporation of Delaware
Filed Apr. 11, 1958, Ser. No. 727,986,
6 Claims. (Cl. 317-1485)
switched by a squarewave input;
FIG. 3 is a schematic diagram of a circuit employing
principles utilized in the present invention, butusing
mechanical switches;
‘
FIG. 4 is a graph of a voltage waveform of the type
produced by the operation of the circuit of FIG. 3; and
This invention relates to arrangements for accurately
controlling ‘the activation of electromagnetic devices. 10
Although not restricted thereto, it is particularly advan
FIG. 5 is a schematic diagram of a circuit embodying
the invention.
' .
Referring now more particularly to the drawing, there
is shown in FIG. 1 an electromagnet energizing circuit
tageous for use in connection with the solenoid actuated
comprising a solenoid L, a resistor R1, a battery E
valves of ‘a fuel injection system for internal combustion
and a single pole, single throw switch S1 all connected
engines of the type disclosed in US. patent application
Serial No. 637,852, ?led February 4, 1957 in the names 15 in series. By closing the switch the solenoid is ener
gized and by opening it the solenoid is deenergized. It
of Robert W. Sutton, Stephen G. Woodward and Curtis
is understood that the solenoid activates a core 6 which
A. Hartman and entitled “Fuel Injection System,” and
may be a valve stem, the solenoid and its core constitut
now Patent No. 2,980,090.
'
ing a bar electromagnet.
In such a system each cylinder of the engine is pro-,
‘In the circuit of FIG. 2 the switch S1 has been re
vided with a solenoid actuated valve, normally closed, to
placed by a transistor TX1 which is shown as being of
which fuel is constantly supplied under pressure. The
the PN? type. The battery E is part of a series circuit
solenoids are sequentially energized, to open the valves, ‘
by means of rectangular voltage impulses derived from
including solenoid L, resistor R1, the collector and emit
a multivibrator or other pulse forming circuit.
ter of transistor TX1, and a resistor R2. *The base of
TX1 is connected to an input terminal 2 and through
a resistor R3 to the positive terminal ofv the power
The
multivibrator is triggered in synchronism with engine
rotation and its output pulses are applied sequentially to
the valves for the various cylinders by a distributor like
wise driven in synchronism with engine rotation.
In some instances the output impulses of the multi
source E.
The resistors R1, R2 and R3 have values so selected
that the transistor is normally non-conducting, thus act
vibrator are of suf?cient power to activate the valve sole? 30 ing- as an open switch. Upon the. application to the
terminal 2 of a negative-going squarewave as shown at
noids directly. In many cases, however, such multi
vibrator output power is not feasible and there must be
employed a switching mechanism actuated by the output
3, the transistor becomes conductive and remains so for
' the duration of the impulse 3.
This amounts to a clos
of the multivibrator or by some other means operated in
ing of a switch in the energizing circuit and the electro
This switching means can be made electronic, which is
desirable, by the use of a transistor circuit. In switching
It is evident that all current necessary for lifting the
core of the electromagnet must be supplied by transistor
amount of the solenoid energizing current must pass
through the transistor. 'This requires the use of anex
duration of the impulse‘3. This requires a power-type
transistor at TX1 and entails all the problems of size,
synchronism with engine rotation, to apply power from 35 magnet is fully energized for the‘duration of the im_
pulse, receiving the full flow of the energizing current
another source to the solenoids in the proper sequence as
; for the total time. ~
dictated by the distributor.
circuits of this type known to the art, however, the total 40 TX1 and that this level of current persists throughout the
cost and heat dissipation which occur in connection with
transistors which -can handle high currents and dis
It is an object of the present invention to provide a
45 sipate large amounts of power.
'
. transistorized switching circuit capable of effecting the
It is a characteristic of solenoid actuated devices, in
energization of a solenoid from a power source for the
cluding valves, that the minimum current which will
duration of a selected time interval by the passage of the
maintain the device in an activated state, or hold the
energizing current through the transistors for only a
valve open, if it is a valve, is considerably less than the
small portion of the interval.
'
minimum current which will open the valve or actuate
It is another object of the invention to provide such a
the device from the closed or inactive position. This
circuit which will be less expensive than‘switching cir
fact is made use of in connection with the invention.
cuits requiring power-type transistors.
The'minimum hold-open current may be designated at
These, and other objects and advantages of the in
1,1 and the minimum opening current as Ivz. If a bias
vention are realized in a circuit in which the solenoid is
current 1V3, such that IVZ>IV3>IV1 is caused to ?ow con- '
constantly subjected to a biasing current from the power
pensive, power-type transistor for this service.
source through a resistor, which current is not sufficient
to move the valve to its activated position but is suf
tinuous-ly through the solenoid winding the valve will
iicient to maintain it in that position once it has been
activated by a higher surge of current. An energy stor
age element such as a capacitor is connected to the
junction of said solenoid and resistor and connected to
solenoid current is modi?ed.
remain in either its open or closed position until the total
1 ‘ 7
Assume that the valve is normally. closed, and that
bias current 1,3 is present. If a positive current pulse
Ia>(l'v2—Iv3) is applied to the solenoid, the valve will
open and remain open after the termination of current
pulse 1,, since bias current Iva' is still present. Should a
switch in parallel with said resistor and to the other ter
minal through a second transistor switch in parallel with 65 negative current pulse Ib> (Iv3--Iv1) be applied, the valve
will close and will remain closed since Iv3<Iv2. FIG. 4
said solenoid. The output of a multivibrator or other
illustrates the desired current waveforms. The. effective
squarewave source is applied by differentiating and recti
valve open time is the period tb—t,,.
.
fying networks to said transistor switches.
FIG. 3 shows a circuit using mechanical switches which
In the drawing:
FIG. 1 is a schematic'diagram of a circuit of the type 70 is capable of providing they waveform of FIG. 4. The
solenoid L is connected in series with resistor R2 and
normally used to operate a solenoid actuated valve or
the source E. A capacitor CZ‘is connected across re_
similar device utilizing a mechanical switch;
one terminal of the power source through a'transistor
m,
3,021,454;
At
sistor ‘R2 through a single pole, single throw switch S2.
a biasing current ?ow through said electromagnet tend~
ing to activate the core thereof, said resistor having
such resistance that said biasing current is insufficient
The capacitor is also connected across the solenoid L
through a second switch S3.
In the operation of the circuit of FIG. 3, the bias
current L3 is supplied by the electromotive force es
tablished by B through R2. If the switch S2 is closed,
to move said core to its activated position but is su?i
cient to maintain said core in said activated position,
a capacitor, means for applying voltage impulses to said
circuit, means responsive to a voltage impulse of a ?rst
sense to momentarily establish a ?rst conductive path
the charging current through capacitor C2 will serve as
the current pulse Ia, to activate the valve. Switch S2
may be opened at any time after I, becomes equal to
connecting said capacitor in charging relation in series
or greater than M, since the solenoid will remain ener 10 with said source and said electromagnet in a sense such
gized due to the presence of the bias current L3 and the
that current ?ows through said electromagnet incident
valve will remain in its activated position.
to the charging of said capacitor is in aiding relation
The condenser C2 will hold its charge until switch S3
ship to said biasing current, the resistance of said path
is closed, whereupon the discharging current will form
being such that the sum of said biasing and charging
pulse 1,, which will partially deenergize the solenoid. 15 currents is sufficient to activate said electromagnet core
Switch S3 may be opened at any time after ‘1b becomes
to said activated position, means responsive to a voltage
equal to or less than Ivl since the valve will then have
impulse of a second sense to momentarily establish a sec
returned to'its rest position.
ond conductive path connecting said capacitor in dis
7
charging relation in series with said electromagnet in a
cuit of FIG. 3. The capacitor C2 is connected in series 20 sense such that current flow through said electromagnet
with transistor TX2 and Rli- across resistor R2‘ and in
incident to the discharging of said capaictor is in oppos
series with transistor TX3 and R5 across the solenoid.
ing relationship to said biasing current thereby reduc
Transistor TX2 is of the PNP type and TX3 is of the
ing the current ?ow through said electromagnet to a
NPN type. The input terminal 2 is connected to the
value which is insufficient to maintain the activated posi
base of TX2 through a capacitor C3 and a diode D1 25 tion of said electromagnet core.
in series. It is also connected to the base of TX3 through
2. A circuit for activating an electromagnet having a
a capacitor C4 and a diode D2, in series. The termi
core movable from a position of rest to an activated
nals of D1 are connected by resistors R8 and R6, re
position, comprising: a source of electromotive force,
spectively, to the positive terminal of the source E, while
means including a resistor connecting said electromagnet
the terminals of D2 are likewise connected by resistors 30 in series with said source in a sense such as to establish
R9 and R7, respectively, to the negative terminal of the
a biasing current ?ow through said electromagnet tend
FIG. 5 illustrates a transistorized version of the cir
ing to activate the core thereof, said resistor having
such resistance that said biasing current is insufficient
source.
Upon the application of the square pulse 3 to the ter
minal 2 it is diiterentiated by the capacitor C3 and R8
to form the waveform shown at 4, which is applied to
to move said core to its activated position, a capacitor,
means responsive to a vonage impulse of a ?rst sense
the diode D1. The diode passes only the negative spike
which coincides in time with the leading edge of the
to momentarily establish a ?rst conductive path comiect
pulse 3. The transistors TX2 and TX3 are normally
non-conductive due to the voltages from the source E
said source and said electromagnet in a sense such that
ing said capacitor in charging relation in series with
current flow through said electromagnet incident to the
to which they are subjected. The negative spike renders 46 charging of said capacitor is in aiding relationship to
TX2 conductive long enough to charge C2 with the cur
said biasing current, the resistance of said path being
rent pulse I,,. The current ?ow 1,, through the electro
such that the sum of said biasing and charging currents
magnet incident to the charging of the capacitor C2 is
is suf?cient to activate said electromagnet core to said
in aiding relationship to the biasing current 1,3 such that
activated position, means responsive to a voltage im
the sum of said currents is suf?cient to activate the elec
pulse of a second sense to momentarily establish a sec
tromagnet core. At the termination of the negative
spike the transistor again becomes non-conductive and
ond conductive path connecting said capacitor in dis
charging relation in series with said electromagnet in a
sense such that current ?ow through said electromagnet
incident to the discharging of said capacitor is in oppos
the current through the electromagnet drops to the Iva
value which maintains the electromagnet core in its acti
vated position.
The elements ‘C4 and R9 also differentiate the wave
form 3 into a waveform 5 identical with 4. This is ap
plied to the diode D2 which is so poled as to pass only
the positive spike which coincides in time with the trail
ing edge of the pulse 3. This renders the transistor TX3
conductive for ‘its duration, discharging C2 to provide
the current pulse 1],. The current flow ‘lb through the
electromagnet incident to the discharge of the capacitor
is in an opposing relationship to the biasing current 1V3
50
ing relationship to said biasing current thereby reduc—
ing the current ?ow through said electromagnet to a
value which is insu?icient to maintain the activated
position of said electromagnet core, means for applying
a rectangular voltage impulse to said circuit, means dif
ferentiating said rectangular voltage impulse to derive
voltage impulses of opposite sense from the leading and
trailing edges thereof, means applying the voltage im
pulse coincident With said leading edge to said means
establishing said ?rst path and means applying said volt
age impulse coincident with said trailing edge to said
such that the sum of said currents is less than In and
thus is insut?cient to maintain the electromagnet core in 60 means estahilshing said second path.
3. A circuit ‘for controlling the operation of a valve
an activated position.
The duration of the spikes of the waveforms 4 and 5
which is biased toward and normally occupies a ?rst po
is determined by the values of the RC elements R8, R9,
sition and is movable by the energization of a solenoid
C3 and C4. This also governs the duration of the con
to a second position, said circuit comprising: a source
ductive intervals of: the transistors. The amount of 65 of electro-motive force, means including a resistor con
charging and discharging current (the magnitude of the
necting said solenoid in series with said source in a sense
pulses 1,, 1b), is controlled by the values of resistors
such as to establish a biasing current ?ow through said
R4, R5, R6, and R7.
solenoid tending to move said valve to said second po
I claim:
70 sition, a capacitor, means including a switch connecting
1. A circuit for activating van electromagnet having a
said capacitor across said resistor, said switch normally
core movable from a position of rest to an activated
‘ eing open and being responsive to a voltage impulse of
positon, comprising: a source of electromotive force,
a ?rst polarity to close, said last named means connect
means including a resistor connecting said electromagnet
ing said source to simultaneously charge said capacitor
in series with said source in asense such as to establish
and to provide suf?cient energizing current through said
3,021,454
solenoid to move said valve to said second position, and
6
said solenoid to move said valve to said second position,
other means including a second switch connecting said
and‘ other means including a second switch connecting
capacitor across said solenoid, said second switch nor
mally being open and being responsive to a voltage im
‘said capacitor across said solenoid, said second switch
normally being open and being responsive to a voltage
pulse of a second polarity to close, said other meanscon
impulse of a second polarity to close, said other means
necting, said capacitor to discharge and simultaneously
provide su?icient drop in the biasing current through
connecting said capacitorto discharge and simultaneously
provide su?icient drop in the biasing current through
said solenoid that said valve moves to said ?rst posi
said solenoid that said valve moves to said ?rst position, ~
and means sequentially applying voltage pulses of said
?rst and second polarity to said switches.
10
4. A circuit ‘for controlling the operation of a valve
which is biased toward and normally occupies a ?rst
position and is movable ‘by the energization of a sole
tion, said ?rst and second switches comprising a ?rst
and second transistor respectively, means connecting said
transistors to said source in a manner to render them
non-conductive, means applying a rectangular voltage
wave to said circuit, means deriving from the leading
noid to a second position, said circuit comprising: a
and trailing edges of said wave voltage impulses of said
source of elcctro-motive force, means including a'resistcr 15 ?rst and second polarity respectively, and means apply
connecting said solenoid in series with said source in a'
ing said impulses respectively to said transistors in a
sense such as to establish a biasing current ?ow through
manner to render said respective transistors conductive
said solenoid tending to move said valve to said second
for the duration thereof.
position, a capacitor, means including a switch connect
6. A circuit for ‘energizing an electromagnet‘ having
ing said capacitor across said resistor, said switch n0r-~
a core movable from a position of rest to an activated
a i
mally being open and being responsive to a voltage im- , 7 position, comprising: a source of electro-motive force,
pulse of a ?rst polarity to close, said last named means
a means including a resistor connecting said electromagnet
connecting said source to simultaneously charge said ca
in series with said source, said'resistor having such re
pacitor and to provide su?icient energizing current
sistance thatv the current ‘?owing through said electro
through said solenoid to move said valve to said second 25 magnet is insufficient to move said core ‘to its activated
position, and other means including a second switch con
position but is sufficient to maintain said core in said
necting said capacitor across said solenoid, said second
switch normally being open and being responsive to a "
voltage impulse of a second polarity to close, said other
means connecting said capacitor to discharge and simul 30
switch connecting said capacitor across said resistor,
taneously provide su?icient drop in the biasing current
tangular voltage impulse to the circuit, means respon
through said solenoid that said valve moves to said ?rst
esive to the leading edgeyof said rectangular'voltage im
position, and means sequentially applying voltage pulses
, said electromagnet core to the activated position and to '
35
tangular voltage wave to said circuit, means deriving
from the leading edge of said wave a voltage impulse of
said ?rst polarity and means deriving from the trailing
‘ ~
simultaneously charge said capacitor through said elec
tromagnet, and means responsive to the trailing edge of
said rectangular voltage impulse to momentarily close
said second switch to deactivate said electromagnet core
and allow said core to return to the rest position and
edge of said wave a voltage impulse of said second po
larity.
means including a second switch connecting said capac
itor across said electromagnet, means for applying a rec~
pulse to momentarily close said ?rst switch to activate
of said ?rst and second polarity to said switches, the
last named means comprising means‘ for applying a rec
activated position, a capacitor, means including a ?rst ’
40
5. A circuit'for controlling the operation of a valve
which is biased toward and normally occupies a ?rst po~ ~
sition‘ and, is movable by the energization of a solenoid
further to simultaneously discharge said capacitor through
said electromagnet, the total current ?ow through said
electromagnet incident to the momentary closing of said
second switch being of insu?icient magnitude to su?i
ciently‘ energize said electromagnet' to‘maintain the acti
to a second position, said circuit comprising: a- source of
electro-motive force, means including a resistor connect 45 vation of said electromagnet core.
ing said solenoid in series with said source in a ‘sense
such as to establish a biasing current ?ow through said
References Cited in the ?le of this patent
solenoid tending to movev said valve to said second po
sition, a capacitor, means including a switch connecting
said‘cap‘acitor across said resistor, said switch normal 50
ly being open and being'responsive "to a voltage impulse
UNITED STATES PATENTS
2,764,715
~ ,
2,904,726
,
Lorenz _____________ __ Sept.‘ 25, 1956
Ricketts ____________ .._ Sept. 15, 1959
of a ?rst polarity to close, said last named means con
necting said source to simultaneously charge said capac
itor and to provide su?icient energizing current through
a
481,054
'
FOREIGN
PATENTS
'
Great Britain ____'__,_____ Mar. 4, 1933
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