Note: Descriptions are shown in the official language in which they were submitted.
3~L6
BAc~G~ou~D 0~ THE I~ MTI~I
For many years, it has heen conventLonal practice
in providing for the measurement and adjustment of the ignition
angle of an internal com~ustion engine to provide a mark on the
fly wheel of the engine which can be observed. A skroboscopic
lamp is directed on the fly wheel and is energized by a signal
from the ignition system ~hich causes the strohoscopic lamp to
be energized at a frequency corresponding to the speed of
rotation of the engine. Thus, when such a stroboscopic lamp is
employed to illuminate the fly wheel, the timing mark appears
to be stationary. ~y employing a suitable delay device, it is
possible to delay the energization of the stroboscopic light
with res~ect to the firing of a particular plug so that the
timing mark appears to be at the top dead center position of
the fly wheel. The amount of adjustment required to cause the
timing mark to appear at the top of the flv wheel is then
employed to provide an indication of the ignition timing.
These previous arrangements have a num~er of
disadvanta~es. In the first place, the timing mark is not
readily visible due to the accumulation of dirt on the fly wheel
and it is necessary to scrape the ~ly wheel to making the timing
mark visi~le. In the second place, the operation described
above basically requires a manual operation, namely the~`
adjustment of the delay device until the timing mark appeared
at the top. Furthermore, since different operators may have a
different opinion as to when the timing mark is at the top, the ~ "
measured timing angle can vary from operator to operator.
As a result of these difficulties, it has heen in-
creasingly common to provide the engine with some device for
producing an electrical pulse when the cran]cshaft is in a
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predetermined position. sy comparing the position of this
pulse with the position of a pulse derived from the voltage
applied to a particular plug, such as the "No. 1" plug of the
engine, it is possible to determine the amount of angular dis-
placement of the ignition. Unfortunately, the different manu-
facturers place magnetic pulse generators res,ponsive to the
position of the fly wheel at different points with respect to
top dead center. This is partly due to the physical limita-
tions in the placement of the magnetic pulse generator due to
auxiliary equipment being employed. It is also due, in part,
to the fact that different engineers have different opinions
as to the most desirable location for such a magnetic pulse
generator. As a result, if a timing measurement device is to
be used with different types of automobile engines, some means
must be provided for correcting for these differences in place-
ment of the magnetic pulse generator, this displacement
commonly being referred to as the reference angle.
It is also obviously necess~ry if apparatus is to
be used with different engines for there to be some means for
satisfactorily calibrating the reference angle correction
means to insure that the correction introduced corresponds
with the actual change in reference angle.
SUMMARY OF THE PRESE~T INVE~TIO~
~ he present invention is con~erned with apparatus
for measuring ignition timing in which a series of pulses are
produced which are of constant amplitude but of a width
dependent upon the ignition timing, these pulses being inte~
grated and applied to an indicating device to indicate the
ignition timing and in which there is means for algebraically
adding to the pulses a correction voltage dependent upon the
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reference angle between the occurrence of a signal from a
magnetic position sensor and the top dead center position
of the piston.
The correction voltage may be a DC voltage and this
voltage may be obtained from an adjustable voltage divider
connected across a known source of Dr voltageO
The adjustable voltage is not only algebraically
added to the pulses but may also be applied to a m~ter which
is calibrated '~n degrees of angular displacement of the refer-
ence angle.
The indicating device for indicating the amount ofignition advance may be a meter which is designed to indicate
the angular displacement in degrees between the energization
of the igniter and the top dead center position of the piston.
The apparatus may be designed for use with an engine
in which the position pulse generating means is so located as
to produce the pulse a predetermined angular distance after the
top dead center position of the piston. This angular distance
is preferably greater than any angle of retardation of the
ignition timing so that the pulse derived therefrom is always
subsequent to the pulse from the connection to the igniter.
Thus, when the correction voltage for correcting for the refer-
ence angle is subtracted from the reference pulses, the result-
ing voltage will indicate the degree of ignition displacement
regardless of whether the ignition is advanced or-retarded.
It is further contemplated that there be calibrating
means involving the use of two periodically varying voltages
one of which is obtained from a source of power of known fre-
quency and the other of which is derived ~rom the first voltage
through a frequency divider so that there is always a known
frequency relation between the two voltages. By this means,
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it is possible to obtai~n a definite angular relation between
the half cycles of the two periodically varying voltages and
the apparatus can be calibrated to indicate this angular
relationship. The voltage of known frequency can be derived
from an ordinary commercial source of power.
The invention further contemplates a novel method
of measuring ignition timing which involves deriving pulses of
varying width depending upon the degree of ignition advance
and algebraically adding to these pulses a voltage dependent
upon the reference angle between the engine cranksha~t position
sensor and the top dead center position. The method further
involves the application to the same timing apparatus as is
employed for measuring the amount of ignition advance, two
voltage pulses spaced apart by a distance determined by the
frequency of one periodically varying voltage and at a fre- ;
quency determined by that of a second periodically varying
voltage having a lower frequency which has a predetermined
frequency relationship to the first periodically varying
voltage.
In accordance with a specific embodiment, apparatus
for measuring the ignition timing of an internal combustion
enginq having a rotating crankshaft, a piston driven thereby, ~i
electrical signal generating means located adjacent a rotating
member driven by said crankshaft to indicate when sald crank-
sha~t is in a predetermined position, an igniter, and means
for periodically energizing said igniter, said apparatus
comprises means adapted to be connected to said igniter to
produce a first electrical signal when said igniter is energized,
means adapted to be connected to said electrical signal generat-
ing means to produce a second electrical signal when said
crankshaft is in a predetermined position subsequent to the top
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dead center position of the piston by an angular displacement
which is constant for any one engine but which varies with
engines of different manufacturers, a timing device effective
upon the application of an input signal to a first input
terminal thereof to initiate a pulse of predetermined amplitude
at the output terminal of said timing device and upon the
application of an input signal to a second input terminaL thereof
to terminate said pulse, means for applying said first electrical
signal to said first input terminal of said timing device and
said second electrical signal to said second input terminal of
said timing device to produce at the output terminal thereof a
plurality of pulses each of a width corresponding to the time
existing between said first and second electrical signals, an
indicating device, means for applying to said indicating device
a signal dependent upon the integrated output of said pulses to
cause said indicating device to indicate the timed relationship
between energization of said igniter and the top dead center
position of said piston, and a correction means for algebraically
adding to said pulses a voltage dependent upon the reference angle
~0 between the occurrence of said second electrical signal and the
said top dead center position of the piston.
From a different aspect, and in accordance with the
invention, a method of measuring the ignition timing of an
internal combustion engine having a rotating crankshaft, a piston
driven thereby, electrical signal generating means located
adjacent a rotating member driven by said crankshaft to indicate
when said crankshaft is in a predetermined position, an igniter,
and means for periodically energizing said igniterl said
method comprises obtaining from a oonnection to said igniter a
first electrical signal when said igniter is energized, obtaining
from a connection to said electrical signal generating means a
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second electrical signal when said crankshaft is in a pre-
determined position subsequent to the top dead center position
of the piston by an angular displacement which is aonstant for
any one engine but which varies with engines of different
manufacturers, producing ~rom said first and second electrical
signals a plurality of pulses each initiated upon the
occurrence of said ~irst signal and terminated upon the
occurrence of said second signal so as to be of a width corres-
ponding to the time existing between said first and second
electrical signals 9 and applying to an indicating device a
signal dependent upon the integrated output of said pulses to
cause said indicating device to indicate the timed relationship
between energization of said igniter and the top dead center
position of said piston, and algebraically adding to said pulses
a voltage dependent upon the reference angle between the
occurrence of said second electrical signal and the said top
dead center position of the piston to adjust for the reference
angle of the engine being testedO
Various other objects of the invention will be
~o apparent from the accompanying specification, claims, and
drawing.
BRIEF DESCRIPTIO~ OF THE DRAWIMG
Figure 1 is a schematic view of my improved
apparatus shown in connection with the ignition system o a
multi-cylinder internal combustion engine,
Figure 2 is a diagram showing the waveforms at
various points in the circuit of Figure 1,
Figure 3 is a view of a portion of the panel
of the housing ~or housing the apparatus schematically shown
in Figure 1, and
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Figure 4 is a portion of the panel of Figure 3
shown on a larger scaleO
DESCRIPTIO~ OF THE PREFERRED EMBODIMENT
Referring first to Figure 1, I have shown schematic-
ally the ignition timing apparatus of the present invention
connected to an automobile ignition system. Referring to this
automob~le ignition system, which has been illustratively
shown in connection with a six cylinder engine, numeral 10
indicates a usual ignition coil having a low voltage primary 11
and a high voltage secondary 12. The low voltage primary
winding 11 is connected to the positive terminal of the
automobile battery 13 through a switch 14 which can be the
conventional "ignition" switcho Current flow from the positive
terminal of battery 13 through primary winding 11 is controlled
by a circuit interrupter 16, having a ground connection 24. The
circuit interrupter is effective to interrupt periodically the
current through the winding 11 in synchronism with the rotation
of the crankshaft of the engine. Commonly, this may take the
form of breaker points which are periodically opened and closed.
~0 I~ recent years, where electronic ignition is employed, this
circuit interrupter may involve a magnetic rotor having a
number of teeth corresponding to the number of cylinders of
the engine and which generates a series of pulses. These in -~
turn control an electronic switch controlling the connection
of the primary winding 11 to ground. The present invention can
be employed with any type of circuit interrupter.
The rotary element of the circuit breaker 16 driven
by the engine is, in turn, connected through any suitable means
to the distributor arm 20 of the distributor 21. The distributor ;
arm 20 makes one complete revolution for each complete cycle
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o~ the engine which involves two complete rotations o~ the
crankshaft of the engine. Each time that the circuit inter-
rupter 16 is effective to interrupt current flow through the
primary winding 11, an abrupt chang~ occurs in the primary
winding to cause a high voltage to be induced in the secondary
winding 12. The upper terminal of secondary winding 12 is
connected through a conductor 25 to the rotor 20. Rotor 20
is in turn adapted to make conductive connection with six
distributor contacts 26, one for each cylinder of the engine.
These distributor contacts are distributed uniformly around
the distributor and are connected to six igniters 30-35 which
are shown specifically as spark plugs. As the distributor
rotor 20 moves into conductive relationsnip with any one con-
tact 26, a firing voltage is applied to that one o the spark
plugs 30-35 to which that particular contact is connected.
The rotatable element of the circuit interrupter 16 and the
distributor rotor are so connected that the high voltage pulses
appearing in secondary winding 12 occur at approximately the
times that the distributor rotor engages the contacts 26. Thus,
as the distributor rotor rotates, being driven by the engine,
a iring voltage is successively applied to plugs 30-35 in
sequence. It is to be understood that each of these spark
plugs 30-35 is associated with a different cylinder. While
I have shown the spark plugs as located in a continuous row,
it is to be understood that they are associatad with the
cylinders in such a manner as to produce a desired firing
sequence. Furthermore, while I have specifically shown spark
plugs, it is to be understood that other forms of igniters may
be employed.
Turning now to the engine diagnostic apparatus, the
reference numeral 40 is employed to indicate a timing device.
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This timing device can be any suitable type which, upon the
reception of a first voltage pulse, will initiate a voltage
output of a predetermined amplitude which continues until
the reception of a second pulse. In this respect, the unit
acts as a "flip-flop" pulse generator. In the specific
aparatus snown, I have employed a 555 linear integrated circuit.
This circuit is designed to function as a timing circuit.
Referring to tne conventional terminals of such a 555 inte-
grated circuit, terminals 41, 42, 43, 44, 45, 46 and 47 are
respectively the trigger, reset, output, power supply, ground,
threshold and control voltage terminals, respectively. The
power supply terminal 44 is connected to a conductor 49 leading
to a suitable positive source of voltage such as a +15 V source.
The ground terminal ~5, along with the threshold terminal 46,
is connected to a ground conductor 50 connected to ground at
51. The control voltage terminal likewise is connected to
ground, being connected in this case through a capacitor 52
whicn in one pàrticular embodiment was a .01 microfarad
capacitor. Similarly, a capacitor 53 is connected between
20 the power supply terminal 44 and ground to filter out any ~`
e~traneous voltage signals from the power supply line 49.
The voltage applied to the trigger terminal 41, which
initiates the voltage pulse, is obtained from the connection
to a predet~ermined igniter such as igniter 30 which may con-
stitute the "No. 1" plug. The reference numeral 60 is employed
to indicate a clamp-on connector which surrounds the ignition
lead extending from the plug 30 to the associated distributor
terminal 26. Plug 30 is the "No. 1" plug in that it is the
first in the firing sequence to have an igniting voltage applied
thereto. The connector 60 is preferably an inductive connector
which has a voltage induced in a coil thereof each time a
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firing voltage is applied to plug~. This voltage is shown
in waveform A of Figure 2. It will be noted that there is an
initial peak voltage followed by an oscillatory discharge. This
voltage is transmitted through a conductor 61, a selector
switch 62 (to be presently described), a conductor 64, a
resistor 65 and a capacitor 66 to the base of an NPN transistor
67. ~ capacitor 68 is connected between right hand terminal of
resistor 65 and ground and tends to bypass the high frequency
components of the pulses picked up by the connector 60. The
resistor 65 serves to attenuate the signal received by the
pickup prior to its being applied to the base of transistor 67.
The capacitor 66 serves to differentiate the signal and insure
~hat only a high voltage peak is applied to the base of tran-
sistor 67. Connected between the base of transistor 67 and
ground is a resistor 69 which normally, in the absence of a
signal, maintains the base at ground potential to prevent flow
of current between the collector and emitter of the transistor.
Thus, depending upon the position of the switch 62, whenever a
pulse is received by the connector 60, a sharp pulse is applied
20 to the base of transistor 67 to cause it to become conductive.
The collector of transistor 67 is connected through a resistor
70 to the po~er supply conductor 49 and the emitter is con-
nected to ground conductor 50. The collector is also connected
throu~q~h a resistor 73 to the trigger terminal 41 of the timer
40. A capacitor 74 is connected between the right hand ter-
minal of rèsistor 73 and ground to filter out any high frequency
components that might be present in the signal appearing at the
collector of transistor 67. The result of the circuit just
traced is that whenever the connector 60 receives a pulse as
the result of the energization of the "No. 1" pluq 30, a neqa-
tive qoinq pulse is applied to the tri~qer terminal 41, These
pulses are in waveform B of Fiqure 2 and are identified by the
3~L46
reference numeral 75. The reason why the pulse is neqative qoinq
is that the output of the transistor 67, upon a positive pulse
being applied to the base, is negative due to the voltage drop
across resistor 70 interposed between the collector and the
positive side of the power line.
- Turning now to the switch 62 which was briefly men-
tioned earlier, this switch is a switch with a plurality of
movable switchblades connected to a common actuator and is
provided for the purpose of switching between an operating and
a calibrating condition. The switch assembly 62 comprises
three movablè switchblades 76, 77, and 78, all of which are
mechanically interconnected and movable as a unit. The switch-
blade 76 is shown in engagement with switch contacts 79 and 80
and is movable into engagement with contacts 80 and 81. Similarly,
switchbladè 77 is shown in connection with contacts 82 and 83
and is mobable into engagement with switchblades 83 and 84.
Swi.tchblade 78 is likewise shown in engagement with contacts
85 and 86 and is movable into engagement with contacts 86 and
87. The switch contacts 76, 77 and 78 are shown in the "oper-
ating" position. When they are moved upwardly so as to be inengagement with contacts 81, 84 and 87, respectively, they are
in their "calibration" position. Thus, ln the "operating"
position shown, a circuit is established between conductor
61 leading from the connector 60 through contacts 79, switch~
blade 82 and contact 80 to the conductor 64 leading to the
base o transistor 67.
Turning now to the input to the reset terminal 42
of timer 40, this is obtained from a signal dependent upon the
position of the flywheel of the engine. The flywheel has been
indicated schemat;cally in the drawinq by the refe~ence numeral
90. It will be noted that this flywheel has a notch 91 therein.
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It will be appreciated that the size of this notch relative to
that of the flvwheel has been exaqqerated for claritv of
illustration. The flvwheel is secured to the crankshaft and
makes two revolutions for each revolution of the distributor
arm 20. Located adjacent to the flvwheel and in inductive
relation therewith is an inductive coil 92~ This inductive
coil is connected to the input terminals of an amplifier 93
having a power supply terminal 94, an output terminal 95, and
a ground terminal 96. The coil 92 and amplifier 93 are nor-
mally in a common housing of the pulse generating unit. Theground terminal 96 of amplifier 93 is connected to a ground
conductor 98 which, in turn, is connected to ground at 99.
The power supply conductor 94 is connected through a conductor
102 and a resistor 103 to a line 100 whicn is in turn connected
to conductor 49 and hence to the +15 V power source. Connected
between conductor 102 and ground is a Zener diode 101 which has
a breakdown voltage of 4.7 V. Thus, a voltage of 4.7 V is
maintained on the input terminal 94 of amplifier 93, the
remaining portion of the 15 volts occurring as a voltage drag
in resistor 103.
Each time that the notch 91 passes the inductive
coil 92, a pulse is generated in the coil 92 which pulse is
amplified to produce a positive pulse 104 shown in the waveform
C in Figure 2. It will be noted that there are two of these
pulses 104 for each of the ignition pulses shown in waveform A.
The reason for this is that the crankshaft makes two revolutlons
for each revolution of the distributor. It will also be noted
that each of the pulses 104 is substantially displaced from the
pulses 75 of waveform B formed as a result of the ignition pulses.
Thus, the first of the pulses 104 occurs a substantial time after
the first pulse 75. The angular displacement between the pulse
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104 of waveform C and pulse 75 of waveform ~ is dependent
upon two factors. In the first place, where the timing is
advanced as is normally the case, the spark pulse resulting
in the square wave pulse 75 occurs a substantial time before
top dead center. In addition, the pickup 92 is so located that
the pulse generated thereby occurs a substantial period of time
after a piston of the No. 1 cylinder reaches top dead center.
This displacement between the top dead center position and the
angular position at which the pulse is produced by the coil 92
is ealled the reference angle. It varies with different cars
depending upon the various factors determined to be desirable
by the manufacturer. In some cases, the reference angle is only,
10. In other cases, it can be as much as 52 1/2 or even 135
The voltage across output terminal 95 wnich, as
previously pointed out, is in the ~orm of a series of pulses
104 is applied across a capacitor 106 which acts as a filter
eapaeitor to filter out any high frequency components of the
signal. The resulting voltage is in turn applied across a
relatively high resistor 107. The upper terminal of resistor
107 is eonnected through a relatively low value resistor 112,
a eonductor 108, eontact 85 of switch 62 when the switch 62 is
in the,"operating" position, slider 78, contact 86, and conductor
109 to the upper terminal of a further capacitor 110. The
voltage appearing aeross capacitor 110, which aets further to filter
out any high frequency components in the signal, is applied through ',
a resistor 111 to the noninverting input terminal 115 of an
operational amplifier 114. The operational amplifier 11~ is an
integrated amplifier and preferably of the t~pe commercially
sold as a ~A 741 operational amplifier. This amplifier has, in '
addition to the noninverting input terminal 115, an inverting
input terminal 116, a positive power supply terminal 117, an
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output terminal li8, dnd d ~ dLive po~er sUp~iy Lerminal 119~
The positive supply terminal 117 is connected to conductor 100
which, as previously explained, is connected to a +lS V power
supply source. The negative power supply terminal 119 is
connected to a conductor 121 which, in turn, is connected to a
-lS V source of power. A capacitor 126 is connected between
posltive supply terminal 117 and ground and a caPacitor 122 is
connected between negative power supply terminal and ground. The
capacitors 126 and 122 are provided to by-pass any undesired high
frequency components. There is also a feedback connection from
the output terminal 118 through a resistor 123 to the inverting
input terminal 116. The inverting input terminal 116 is also
connected through a resistor 125 to the ground conductor 98.
The gain of amplifier 114 is dependent upon the relative values
of resistors 123 and 125. In one typical case, resistor 123 had
a resistance of 12 kilohms while resistor 12S had a resistance of
only 1 kilohm. Thus, in this case, there was a gain of 12.
The output voltage appearing at terminal 118 which
has been amplified by amplifier 114 is connected through a
blocking capacitor 128 to the base of an NPN transistor 129.
The collector o~ this transistor is connected through a
resistor 130 to the +15 V conductor 100 and the base is also
connected through a resistor 131 to ground so that in the
absence of an input signal from the output of amplifier 114,
t~e base is at ground potential. A filter condenser 132 is
connected in parallel Witil resistor 131 so as to by-pass any
high frequency components that might be present in the output
of amplifier 114.
The result of a positive pulse being applied to the
base of transistor 129 is to cause this transistor -to become
conductive, lowering the potential of the collector by reason
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of the increased voltage drop across resistor 130. The posi-
tive pulse applied to the base of transistor 129 is thus inverted
creatin~ a neqa-tive aoina ~ulse which is a~lied throuah
conductor 134 to the reset terminal 42 of the timer 40. Tne
waveform of the voltaae a~lied to terminal 42 is indica-ted
bv the wave~orm D. It will be noted that this waveform ~
includes a numb~r of negative pulses 136, each corresponding
to one of the positive pulses 104, but merely inverted tnere-
from and, in most cases, of di~ferent amplitude.
Considering the operation of the timing apparatus 40,
it will be recogni2ed from the preceding description that a
negative going pulse is applied to trigger terminal 41 each
time that an ignition pulse is applied to spark plug 30. Simi-
larly, a negative pulse is applied to the reset terminal each
time that the coil 92 senses the presence of the notch 91. The
pulses in question are indicated in Figure 2 by the waveforms ;
and D. The timing apparatus functions so that each time
that a negative pulse is applied to the trigger terminal 41,
an output of a predetermined amplitude will appear at output
terminal E. This output voltage will continue until a negative
pulse is received at the reset terminal 42 at ~hich time the
voltage of the output terminal E will disappear. The result .
is a series of pulses of predetermined amplitude, the duration :~
o~ these pulses being dependent upon the time between the
application of negative pulses to the trigger terminal 41 and
the reset terminal 42. The resulting pulses appear in waveform
-E of Figure 2 and each pulse is designated by the reference
numeral 140. It will be noted that each pulse 140 is initiated c
at the beginning of the negative pulse 75 of waveform B and is
30 terminated at the beginning of the negative pulse 136 of w~ve- ~
form D. The total magnitude of the pulse 140 thus becomes `:
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a function of the t'me ~etween the fir~ng of the spark plug 30
and the generation of a pulse by the inductive coil 92. ~s will
be pointed out later, the value of these pulses over a period
of time is integrated to determine the timing of the engine.
The output voltage appearing at output terminal 43
of timer 40 is applied through a resistor 1~1 to the inverting
input terminal 145 of an operational amplifier 142. The opera-
tional amplifier, like amplifier 114, can be of the type convention-
ally known as a ~ A741 amplifier and is provided with a nonin-
verting input terminal 144, an output terminal 146, a negativepower supply terminal 147 and a positive power supply terminal
148. The resistor 143 is connected between the output terminal
146 and the inverting input terminal 145 and acts with resistor
141 to control the gain of the amplifier. The gain of the
amplifier is dependent upon the relative values of resistors
143 and 141. In one particular instance, a 15 kilohm resistor
was employed for resistor 143 and a 10 kilohm resistor for
resistor 141 giving the amplifier a gain of 1 1/2. It will
be noted that the positive power supply terminal 148 is con-
~ nected to the +15 V conductor 49 and the negative power supplyterminal 147 is connected through conductors 152 and 153 to
the same -15 V source of power as is conductor 121, previously
referred to in connection with amplifier 114. A capacitor 149
is connected between the negative power supply terminal 147 and
~round to filter out any extraneous high frequency components.
The amplifier 142 not only acts to amplify the voltage pulses
from the timer 40, but also serves to invert them so that the
output appearing at output terminal 146 is indicated by the wave-
form F of Figure 2. It will ~e noted that the pulses 150 in
30 s~aveform F are negative. They will have the same pulse width as
pulses 140 of waveform E.
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The pulses at the output terrninal 146 are applied
throu~h a resistor 151 to the inverting input terminal 157
of a further amplifier 156 which is generally of the same
character as amplifier 142. This amplifier has positive and
negative power supply terminals which are respectively con-
nected to conductors 49 and 153 leading to positive and nega-
tive voltage sources, respectively and have capacitors 160 and 161
connected between these power suppl~ terminals and ground.
It also has a noninverting input terminal connected to the ground
conductor 50 as is the case in connection with amplifier 142.
It also has an output terminal 158 and there is a feedback connec-
tion including a resistor 159 between output terminal 158 and the
inverting input terminal 157. Again, the relative values of
resistors 159 and 151 determine the gain of the amplifier. In
this particular case, resistors of the same value were employed
for resistors 159 and 151 so that the amplifier had a unity
gain. The effect of the amplifier, however, is to again
invert the signal so that the output of amplifier 156 is
again a series of positive pulses which are applied through
a conductor 163, a resistor 164, a rheostat 165, a conductor
166, an* the contacts of a selector switch 167 to a meter
168 which has its opposite terminal connected to ground at
169. A capacitor 170 is connected across the meter 168 and
acts to integrate the positive voltage pulses being supplied
to the meter 168 to cause the meter to assume an average
position depending upon the magnitude and relative width o
the`pulses as compared with the time of the engine cycle.
The meter will take up an average position dependent upon
the width of the pulses and hence dependent upon the time
between the firing of the "No. 1" plug and the sensing of
the notch 91 by the coil 92 as related to the time of the
engine cycle. As will be explained later, this meter 168 will
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be calibrated to indicate the degrees of ignition timing. The
rheostat 165 is designed to be adjusted to vary the sweep of
the meter needle as will be described later.
Brief reference has been made to the selector switch
167. This switch is used in connection wi~h meter 168 and
meter 180, to be presently discussed. Meters 168 and 180 are
both designed to be employed for several purposes and the
function of switch 167 is to connect the meters 168 and 180 to
the spark advance measuring mechanism when it is desired to
measure spark a*vance and to disconnect these meters from the
spark advance measuring apparatus when the meters are to be
employed for other purposes. The switch 167 has three movable
switchblades 172, 173 and 17~ which are selectively movable
from the upper position shown to a lower position. In tne
upper position shown, they bridge contacts which serve to
connect the meters 168 and 180 to the ignition advance measur-
ing apparatus. Thus, in the circuit traced through meter
168, the circuit went through the upper contacts in engagement
with the movable switchblade 172. In the lower position of
~0 slidable contacts 172, 173 and 174, they connect meters 168 and
180 to conductors 175~ 176 and 177 leading to signal sources
connected with other types of tests.
The apparatus, as described, would be satisfactory to
measure i~nition advance if the pulse produced by coil 92 oc-
curred at the top dead center position of the No. 1 cylinder.
Unfortunately, as described previously, these pulses occur at
different positions with respect to top dead center depending
upon the particular manufacturer. In some cases, the pulse
occurs as much as 135 after top dead center. If the ignition
advance measuring apparatus is to be used with different vehicles
and i~ it is desired to read the actual amount of ignition
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- advance directly withou-t computation, it is desirable to provide
some means for compensating for the angular distance between
top dead center and the occurrence of the pulse indicative of
flywheel position. This angle is commonly called the
"reference angle". In the present apparatus, this is done by
algebraically adding to the pulses produced by the timer 40 a
DC voltage having a value corresponding to the reference angle.
Referring to the drawing, there is a potentiometer 185 having
a slider 186 and a resistor 187. One terminal of resistor 187
10 is connected through a further resistor 188 to a +15 V power
source whereas the opposite terminal of resistor 187 is connected
to ground. Thus, the resistor 187 has a voltage applied there-
across which is dependent upon the relative values of resistors
187 and 188. In one particular case, an 18 kilohm resistor
was employed for resistor 188 and a 5 kilohm resistor for
resistor 187 of the potentiometer 185. In such case, the voltage
across resistor 187 would be 5/2.3 of 15 V or 3.26 V.
selected portion of the voltage appearing across resistor
187 appears between the slider 186 and ground. The slider
20 186 is connected through a resistor 190 to the noninverting
input terminal 191 of an amplifier 192 which is similar to
amplifiers 142 and 156 in that it is an operational amplifier
which may be of the type commercially sold as a ~ A 741
amplifier. Operational amplifier 192, as with amplifiers 142
and 156, has, in addition to the noninverting input terminal
191, an inverting input terminal 193, output terminal 194 and
positive and negative power suppl~ terminals. The positive
power supply terminal is connected to a ~15 V power source.
The negative power supply terminal is connected to conductor
30 121 whichr as previously explained,-is connected to a -15 V
power source. The output terminal of amplifier 192 is connected
directly to the inverting input terminal 193 of the amplifier.
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3~6
The primary functlon of the amplifier 192 is to isolate the
voltage appearing at the outpu~ thereof from the potentiometer
185 to prevent any danger of feedback. The output of the
amplifier 192 is connected through a conductor 197 and a
resistor 198 to the inverting terminal 157 of amplifier 156.
In other words, the voltage at the output of amplifier 192 is
combined with the voltage from output terminal 146 of amplifier
142. As will be noted from Figure 2, the output voltage of
terminal 146, as shown in waveform F is a series of negative
.10 pulses. The voltage appearing at the output terminal of
amplifier 192 is a continuous DC voltage which is positive with
respect to ground. As a result, this added voltage is opposite
in polarity to the-polarity of the pulses 150. In waveform G,
the effect of this is shown. Assuming that line 200 represents
ground potential, then the voltage appearing between ground - -
potential line 200 and line 201 represents the voltage which
appears at the output of ampllfier 192 and which is combined
with the voltage pulses. It will be readily apparent that if
these two voltages are added, the net effect is to reduce the
integrated output of pulses 150 since the added voltage
between ground line 200 and line 201 is not only opposite in
potential but is continuous whereas the pulses 150 are inter-
mittent in character. Thus, when one starts integrating the
waveform G, the entire area between the ground line 200 and
potential line 201 must be subtracted from the total of the
pulses beneath the ground line 200. The result is that the ,~
integrated value of the current passing through meter 168 will
be substantially reduced and the meter will have a lower reading ~;
than would otherwise be the case. The apparatus is designed so
that the adjustment introduced by the addition of the voltage
from amplifier 192 is sufficient to compensate for the reference
:
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3~
angle so that -the reading o~ meter 168 corresponds to the actual
spark advance.
It is also important that one adjusting the slider
186 of the potentiometer 185 know how much adjustment is --
being effected. For this reason, I have also provided a
meter 180, previously referred to, which, like meter 168, is
located on the front panel as will be discussed later. The
output of amplifier 192 i5 not only applied to the inverting
input terminal of amplifi`er 15~ but is also applied to the
meter 180. When the slidable contacts 173 and 174 of selector
switch 167 are in the upper position which they assume when
magnetic-timing is being measured, the lower terminal of meter
180 is connected through switch contact 173 to ground conductor
98. The upper terminal of the meter is connected through
switchblade 174 to a junction point 207. This jun~tion point
is connected through a rheostat 206 and a resistor 205 to the
output terminal of amplifier 192. The junction point 207 is
also connected through a rheostat 208, a resistor 209 and a t
conductor 210 to conductor 153 which, as previously pointed
out, goes to a -15 V power source. The junction 207 is ~hus
maintained a~ a potential somewhere between the output potential
of amplifier 192 and -15 V depending upon the values of resis-
tors 205, 209 and the setting of rheostats 206 and 208. The
connection to the -15 V source is necessary since the pointer
of meter 180 is biased to a mid-position (because of other
uses to which the meter is put in other tests) and it is
necessary to apply a negative voltage to the meter to insure
that the pointer will be at zero position when no signal is
being received from amplifier 192. The resistor 209, in one
particular embodiment, had a resistance of 17 4 kilohms
~hile rheostat 208 had a ma~imum resistance of 5 ~ilohms. In
' ~ -19- ;
.
.
3~
the same embodiment, rheostat 206 had a maximum resistance of
3 kilohms while resistor 205 had a resistance of only 47 ohms.
The voltage thus applied to meter 180 depends upon the settings
of rheostats 206 and 208. Rheostat 208 is employed for ad-
justing the zero point of the meter. It will be obvious that
as the value of this resistance is decreased, the potential
of junction 207 will shift in a negative direction and it is
possible, in this way, to adjust the meter so that when no
signal is being applied by amplifier 192, the needle of meter
180 will be at the zero position despite being biased to a
mid-position. The rheostat 206 is used to adjust the range of
movement of the meter. It will be obvious that the smaller
the impedance presented by the rheostat 206, the greater will
be the effect of the voltage on the meter 180. Thus, by
moving the slider to the r~ght,the sweep of the needle is
increased. The operation of these two units will be described
later in connection with the calibration of the device. When
properly calibrated, the meter 180 will indicate the amount of
reference angle that has been inserted by adjustment of the
slider 186 of rheostat 185.
This invention also involves a novel calibrating
means. Broadly, this involves generating two signals spaced
apart by an angular distance which has a known relation to
the angular distance of a complete cycle. This is done by
using a source of power of known frequency and then, through
the use of a frequency divider, developiny a second frequency
having a known lower frequency value. If the distance between- --
pulses of the lower frequenc~v is assumed to be 360, then
the distance between pulses of the higher frequency current
30 will be a predetermined ~raction of the distance between the ~
pulses of the lower frequency current. Spaced pulses corres- ;
ponding to the higher frequency current can then be applied
~ -20-
~; - ,, . ' . :; j : -
~933~L~6
to the timing apparatus 40 io develop a serie~ of waveforms
which are integrated~ By suitably adjustin~ the appara-tus so
that the reference angle indicated on meter 180 corresponds
to the ratio between the two frequencies, it is possible to
insure that the apparatus is properly calibrated. The apparatus
and operation of the calibrating means will now be described.
A regular commercial source of power 212 represented
by two line wires is connected to the primary winding of a
transformer 213. The output of the secondary winding is con-
10 nected to a square wave generator 214 of any suitable type,
the output voltage of the primary being selected so as to supply
_a voltage of~the proper magnitude to the input of the square
wave generator. The square wave generator may be of any type
which will, when an alternating current is applied thereto,
have a square wave output. A typical unit of this type is one d
employing initial filtering circuits and a Schmitt trigger for
converting the alternating sine wave into a square wave~ The
output of the square wave generator is applied through a
conductor 215, a resistor 216 and a conductor 217 to the
20 base of a transistor 218. The output of the square wave
generator 214 is also applied to the input of a suitable fre- .
quency divider such as a counter 219 having a ground connection
220. In the particular example being considered, the source
of power is a typical commercial source of power having a 60 Hz.
frequency. The counter 219 generates a pulse output for each
six pulses supplied to it; thus the OUtpllt of counter 219 has
a frequency of only 10 Hz. The output of the counter 219 is
then applied through a conductor 222, contacts 84 and 83, and
movable contact 77 of selector switch 62, conductor 223,
resistor 224 and conductor 225 to the collector of an NPN
transistor 218. In this way, a 10 cycle voltage is applied to
-21-
- ~93~6
the collector and a 60 cvcle voltaqe to the base of transistor
218. Due to the resistor 224, -the emitter becomes negative each
time that the transistor 21~ becomes conductive. This happens
each time tha~ the base is supplied with a positive potential
from the 60 Hz.-source during the positive going portions of the
10 Hz. voltage. This thus occurs six times during each cycle
of the 10 Hz. voltage. If it be assumed that one cycle of the
10 H~. frequency represents one distributor or two complete
en~ine revolutions, which is equal to 720, then each pulse
occurring at the collector oE transistor 218 represents 60.
These 60 pulses appearing at the transistor 218 are
applied to the ~ase of a further NPN transistor 230. The
collector of this transistor 230 is connected through two
resistors 231 and 232 and conductors 234, 235 and 236 to the
conductor 49 leading to the +15 V source of power. The emitter
of transistor 230 is connected through a diode 238 to ground
conductor 24Q. The pulses applied from the collector of
transistor 218 to the base of NPN transis-tor 230 will cause a
series of negative pulses to appear at the collector of tran-
sistor 230. These nega`tive pulses are shown by the waveformin Figure 2 and are designated by the reference numeral
240. The junction of resistors 231 and 232 is in turn con-
nected to the base of a PNP transistor 242 which has its .
collector connected through a resistor 243 to the ground con-
ductor 240. Thus, each time that one of the negative pulses
240 is applied to the base of transistor 242, a posi-tive pulse
is produced at the collector. The positive pulses are indicated
by the waveform I of Figure 2 and are designated by the refer-
ence numeral 245. It will be noted that each of these pulses
has a pulse width one-twelfth of that of the distance between two
successive pulses. Thus, the pulses exist during one-twelfth
~ -22- ~;
~3~L~6
of a cycle of the waveform I. These pulses are in turn applied
through a resistor 246 to the noninverting input terminal of an
operational amplifier 247. This amplifier is similar to
amplifiers 142, 156, 114 and 247. The amplifier has a positive
power supply terminal connected to conductor 236 leading to
the +15 V source and a negative power supply terminal connected
through conductors 248 and 249 to the -15 V source. There is
also a direct feedback connection between the output terminal
250 of amplifier 247 and the inverting input terminal of the
10 amplifier. Due to this direct feedback, the amplifier has a
gain of unity and is primarily provided for the purpose of t
isolating this output from that appearing at the collector of
transistor 230. The leading edges of the pulses appearing at
the output of amplifier 247 which correspond to the leading
edge of pulses shown in waveform I are applied through conductor
252 to the switch contact 81 and, when the slide contact 76
is in the calibrating position, through the contact 80 and
conductor 64 to the resistor 65 which, as previously explained,
is connected to the base of transistor 67. In short, the leading
20 edges of the pulses appearing at the output of operational
amplifier 247 are applied to the base of trànsistor 67 instead
o~ the pulses derived from the connection to the No. 1 spark
plug lead. At the same time, the trailing edge of the pulses
each appearing at the collector of transistor 230 are applied
through conductor 254 to terminal 87 of the selector switch 52
and, when the selector switch is in its calibrating position,
are applied through sliding contact 78, conductor 109, and re-
sistor 111 to the noninverting input terminal 115 of the
amplifier 114. In other words, the pulse obtained from the
30 trailing edge of the pulses 240 is applied to the operation
amplifier 114 in lieu of the pulse derived from the pickup 92.
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~93~
The effect of this is that a pulse is applied to the input
terminal 41 of timer 40 at the time of occurrence of the lead-
ing edge of each pulse 245 and a pulse is also applied to
the reset terminal 4Z of timer 40 at the time of occurrence
of the trailing edge of each pulse 240. It will be clear
that the leading edge of each pulse 245 is spaced from the
trailing edge of pulses 240 by an angular distance corresponding
to the frequency of the 60 Hz. frequency. In other words,
assuming 360 between the leading edges of pulses 245, the
trailing edge of pulses 240 will be spaced from the leading
edges of pulses 245 by an angular distance of 60. The net
effect will be that a series of pulses will be produced at
the output terminal 43 of timer 41, each of which has a
pulse width the equivalent of 60 as measured by the repeti-
tion rate of the pulses. These pulses are amplified by
amplifier 156 and are applied to the timing advance indicator
168 in the same manner as the pulses derived in the normal manner
were applied. It is now possible to calibrate-the unit readily.
Before describing the calibration of the unit, the
panel of Figure 3 will be discussed. The numeral 255 is
employed to indicate generally the front panel of a test
apparatus having many functions besides that of measuring
the timing angle. For example, there is a cathode ray tube,
the screen of which appears in the drawing and is designated by
reference numeral 256. There is also, in addition to the meters
168 and 180 previously discussed, a further pair of meters
257 and 258 which can be employed to indicate various functions.
The meters 168 and 180 are not only designed to indicate
various values in connection with the determination of the
magnetic timing but also to perform other functions dependin~
upon the position of the selector switch 167 previously discussed.
-2~
~,, ,, : . .
~93~6
As shown in E'igure 3, the selector switch is indicated by tne
push button 167. By actuation of this button, the switch is
moved to the magnetic timing position shown in Figure 1.
There are also numerous other selector switches, each actuated
by its own button. For example, the numerals 259 and 260 are
employed to indicate banks of selector switches. Since the
function of these switches play no part in the present inven-
tion, their function is not described. Similarly, there is
a function selector knob 261 which can be rotated to select
various tests to be performed, some of which are indicated on
the screen 256 of the cathode ray tube.
In Figure 4, significant portions of the meters 168
and 180 are reproduced on a somewhat larger scale. It will be
noted that the meter 168 has a legend 263 reading "MAGNETIC
TIMING". Below that is a scale 264 having calibrations begin-
ning with -10 and extending up to 60. The numeral 265
designates a pointer which is movable by a suitable meter
movement over the scale 264.
Referring to the meter 180, this again has a legend
266 which reads "MAGNETIC TIMING REF" meaning that the meter
indicates the magnetic timing reference angle. This likewise
has a scale 267 which, in this case, is calibrated between zero
and 180. As has been pointed oùt, there are reference angles.
which are as large as 135 and the scale is designed to take
care of reference angles up to 180. Movable over the scale
267 is a pointer 268. As previously pointed out, the meter
movement is biased so as to cause the pointer to assume a mid-
position on the scale when the meter movement is deenergized.
This is because the meter 180 has other scales and is used in
connection with other tests.
~ 33~6
CA_ BRATION
Having descri~ed tne meters and the calibration
circuits, it is now possible to describe how the unit is
calibrated. Initially, the calibration switch 62 is moved
to the calibration position. This calibration switch does not
normally appear on the front panel and is primarily intended
to be accessible only at the factory or to the serviceman.
The slider 186 of the potentiometer 185 is now moved to its
extreme left position at which no voltage is being applied
to the input of amplifier 192 and hence no voltage is being
applied from potentiometer 185 to the input terminal 157 of the
operational amplifier 156. In the arrangement shown in Figure
3, the adjusting knob 185 is turned to its extreme counter-
clockwise position. The rheostat 165 is now adjusted until
- the magnetic timing meter 168 indicates a reading of 50~. It -- -
was previously pointed out that the rheostat 165 is designed to ---
adjust the sweep of the meter needle. The knob 185 (or slider
186 of potentiometer 185) is now adjusted SQ as to reduce the ~ -
reading of meter 168 to -10. This is the point of zero -~
deflection of the meter. Potentiometer 206 is now adjusted
so that the meter 180 reads 60. It will be recalled that the
length of the pulses 240 and 245 correspond to 60. The
meter should read 60 under these conditions since the appli- -
cation of the pulses 240 and 245 to the timer 40 causes a
series of pulses which are of a duration equal to one-sixth
of the total cycle. When this is done, the switch 62 can
then be moved to the operating position and thereafter it
will be assured that the meter 180 will correctly indicate
the amount of reference angle which has been introduced and
meter 168 will read the correct amount of timing adjusted for
this reference angle.
-26-
~93~6
VALllES OF COMPONENTS
In the foregoing descrip~ion, reference has been
made to the values of certain components in a typical piece of
apparatus. In the table below, the values of the other
components have been indicated. It is to be understood, of
course, that the invention is in no way limited to the use of
components of a particular value and that the values of the
components given below are intended to be merely illustrative
~ of those successfully used in one embodi~ment of the apparatus.
Resistors Capacitors
65, 70, 107, 10 kilohms 53, 66, 68, .01 microfarad
130, 131, 151, 74, 110,
243 and 246 122, 126,
128, 149,
69 33 kilohms 160 and 161
73 and 112 ` 470 ohms 106 .1 microfarad
103, 111, 190 132 .047 microfarad
and 164 1 kilohm
170 2000 microfarad -~
159 and 198 10 kilohms
165 Max. 2 kiIohms
216 100 kilohms
224 2.2 kilohms
231 and 232 4.7 kilohms
OPERATION ~ ;
While it is believed that the operation of the
apparatus will be clear from the foregoing specification, the
operation will be generally summarized in the following para
graphs.
When it is desired to measure the ignition timing of
a vehicle equipped with a magnetic pulse indicator for indicating
the position of the flywheel, the connector 60 is applied to the
conductor leading from the distributor to the No. 1 spark plug
30. At the same time, connections are made to the coil 92.
Customarily, the pickup including the coil 92 includes the
-27-
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.
~3~l~6 - ~
amp~ifie~ 93 in a unit which has -three terminals ga, 95 and 96.
This unit is designed to have a three terminal connector
connected therewith to make electrical contact with the three
output terminals. The three conductors leading from terminals
94, 95 and 96 in Figure 1 are thus automatically connected to
the magnetic pulse generator.
It will also be assumed that the apparatus has been
calibrated in the manner described under the heading
"CALIBRATION'i and that the switch 62 has been moved to the
operating position shown in Figure 1. Button 167, shown in
the front panel of Figure 3, will now be actuated to move the
switch contacts 172, 173 and 174 to the position shown in
Figure 1. In this position, the meters 168 and 180 are connected
to the portion of the apparatus for measuring the ignition
timing.
The next step is to adjust the potentiometer 185 for
the reference angle of the vehicle being tested. If this
an~e i~not known, it must be determined from a suitable refer-
ence manual for the particular vehicle being tested. The knob -
of potentiometer 185 which controls the position of slider 186is adjusted until the meter 180 indicates the reference angle
in question. When this happens, meter 168 will indicate the
amo~nt of ignition advance or retardation. Summariæing, the
signal from the No. 1 plug, shown in waveform A of Figure 2, is
filtered, amplified and inverted and applied to the input ~`
terminal 41 of timing apparatus 40, the pulses applied to
timer 40 being indicated by the pulses 75 of waveform A of
Figure 2. At the same time, the pulses generated by the
pickup 92 are filtered, amplified and inverted to produce the -
pulses 136 of waveform D of Figure 2, these pulses being
applied to the reset terminal 42 of timer 40. The result will
-28-
!
9;~L4~ - -
be a series of pulses such as puls~s1~0 of waveform E of
Figure 2 which are of constan-t amplitude and which are of a
duration dependent upon the amount of ignition advance and
also on the amount of the reference angle. These voltage
pulses are amplified and inverted in amplifier 142 and appear
as voltage pulses 150 of waveform F of Figure 2. The voltage
employed to compensate for the reference angle and which is
obtained from potentiometer 185,after passing through amplifier
192, is applied as a compensating voltage to the voltage
pulses 150. This voltage is a con~inuous positive voltage and,
as shown in waveform G of Figure 2, tends to oppose the
voltage of pulses 150 and reduce the integrated value thereof.
The resultant voltage is then applied to meter 168 where it
tends to be integrated or averaged out by capaci'tor 170 to
produce a reading of meter 168 corresponding to the average
integrated value of pulses 150 reduced by the integrated value
of the voltage represented by line 201 of waveform G. The
~ ~ . . . .
resultant reading of meter 168 will be a reading of the magnetic
timing irrespective of the amount of the reference angle.
~ CONCLUSION
~ It will be seen that I have provided apparatus which
enables ready adjustment for the amount of the reference angle.
It will also be seen that I have provided a simple means of
calibrating the igni~ion timing measurement apparatus. It will
also be seen that I have provided a timing measurement apparatus
which is extremely simple to use and which can be readily
attached to a vehicle being tested with a minimum of effort.
It will also be seen that I have provided a novel method of
measuring ign~tion timing.
--2g-- :
