United States Patent [191
`Kruncos
`
`[11] Patent Number:
`[45] Date of Patent:
`
`4,950,983
`Aug. 21, 1990
`
`[54] TACHOMETER SIGNAL CONDITIONING
`CIRCUIT
`[75] Inventor:
`
`Francis E. Kruncos, Fond du Lac,
`Wis.
`[73] Assignee: Brunswick Corporation, Skokie, Ill.
`[21] Appl. No.: 391,449
`[22] Filed:
`Aug. 9, 1989
`
`[51] Int. Cl.5 ............................... .. G01P 3/54
`[52] U S Cl ............................ .. 324/169; 307/268
`[58] Field of Search ............. .. 324/166, 168, 169, 170,
`324/225; 307/268, 309; 328/5
`References Cited
`U.S. PATENT DOCUMENTS
`
`[56]
`
`4,637,991 8/1987 Kruncos ............................ .. 324/ 169
`Primary Examiner-Reinhard J. Eisenzopf
`Assistant Examiner-Walter Snow
`Attorney, Agent, or Firm-Andrus, Sceales, Starke &
`Sawall
`
`ABSTRACT
`[57]
`A tachometer signal conditioning circuit (20) includes a
`timer circuit (48) responsive to ignition pulses from the
`primary lead (28) of an internal combustion engine igni
`tion coil (26), and outputting a timing pulse terminating
`after a given time delay interval during which RFI,
`EMI and other transients on the primary lead (28) are
`ignored. A one shot monostable multivibrator circuit
`(56) responds to the trailing edge of the timing pulse and
`outputs a trigger pulse of given duration. A switch
`circuit (66) is connected to the battery circuit (22) and is
`turned on by the leading edge of the trigger pulse'and
`turned off by the trailing edge of the trigger pulse, all
`before the next ignition pulse. The switch circuit (66)
`has a node (80) providing an input for a standard low
`voltage tachometer (82). Conductive and nonconduc
`tive states of the switch circuit (66) change the battery
`circuit voltage at the node (80) at a frequency corre
`sponding to the frequency of the ignition pulses.
`
`7 Claims, 1 Drawing Sheet
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`TOYOTA Ex. 1016, page 1
`Toyota v. Hagenbuch
`IPR2013-00483
`
`

`
`TPatent
`
`Aug. 21, 1990
`
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`TOYOTA Ex. 1016, page 2
`Toyota v. Hagenbuch
`|PR2013-00483
`
`TOYOTA Ex. 1016, page 2
`Toyota v. Hagenbuch
`IPR2013-00483
`
`
`
`
`
`
`

`
`1
`
`TACHOMETER SIGNAL CONDITIONING
`CIRCUIT
`
`10
`
`BACKGROUND AND SUMMARY
`The invention relates to a tachometer signal
`invention relates conditioning circuit for an internal
`combustion engine having a battery circuit and an igni
`tion coil with a primary low voltage lead and a second
`ary high voltage lead.
`The invention arose during efforts to develop a reli
`able and widely usable tachometer for marine drive
`engines, including racing applications. In high perfor
`mance marine engines, the use of nonsuppression spark
`plugs and leads have caused tachometer problems, par
`ticularly RFI (radio frequency interference), EMI
`(electromagnetic interference), and other transients.
`The present invention addresses and solves this prob
`lem.
`The invention adapts most standard tachometers to
`most ignition coils. The invention converts the ignition
`pulse on the primary lead of the coil to a tachometer
`signal transitioning between ground and a voltage level
`in the range of battery voltage, which signal is readily
`usable in most standard tachometers. The ignition coil
`converts a low voltage such as 140 volts on its primary
`lead to a high voltage such as thousands of volts on its
`secondary lead supplying spark plug voltage. The low
`voltage on the primary lead, e.g. 140 volts, is still too
`high for use in standard low voltage tachometers. The
`30
`present invention allows the primary lead voltage to
`operate a low voltage tachometer, e.g. less than 12
`volts.
`The invention cleans up noisy signals such as caused
`by point bounce in breaker point systems. The invention
`eliminates the above noted RFI and EMI problems.
`When used with a high performance marine battery
`capacitor discharge ignition system, the invention elimi
`nates the requirement for a special reverse polarity
`tachometer and allows the use of a standard tachometer
`connected to the 140 volt primary lead of the ignition
`coil that has an extremely fast rise time and short dura
`tion. The invention enables a single standard tachome
`ter to be left in the dash if engines and ignition systems
`are changed. The invention also allows for usage of 45
`various makes of tachometers because of the readily
`usable tachometer input signal provided by the inven
`tion.
`
`25
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`35
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`20
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`4,950,983
`2
`precision timer, where manufacturer assigned pin num
`ber designations are shown to facilitate understanding.
`Timer 48 has an input pin 1 responsive to ignition pulses
`from the coil primary lead. Output pin 7 immediately
`transitions low in response to the ignition pulse, and
`then transitions back high after a given time delay inter
`val during which RFI, EMI and other transients on the
`primary lead are ignored. In the preferred embodiment,
`the given time delay interval of the output timing pulse
`on pin 7 is 1.5 milliseconds, which is set by the RC
`network provided by resistor 50 and capacitor 52. Ca
`pacitor 54 provides an rf bypass ?lter. The output tim
`ing pulse on pin 7 thus has a leading falling edge, and a
`trailing rising edge occuring 1.5 milliseconds after the
`leading edge.
`The trailing rising edge of the noted timing pulse
`triggers a one shot monostable multivibrator 56, pro
`vided by a 4538 one shot monostable multivibrator,
`where manufacturer assigned pin number designations
`are shown to facilitate understanding. One shot mono
`stable multivibrator 56 has an input pin 4 responsive to
`output pin 7 of timer 48, and has an output pin 6 output
`ting an output trigger pulse substantially immediately
`upon receipt of the trailing rising edge of the timing
`pulse from pin 7 of timer 48. The time duration of the
`trigger pulse at output pin 6 is set by the RC network
`provided by resistor 58 and capacitor 60, and is chosen
`according to engine rpm. In the preferred embodiment,
`for marine racing engines having engine speeds typi
`cally approaching 8,000 to 9,000 rpm, the time duration
`of the trigger pulse on output pin 6 is 0.1 milliseconds,
`which is an order of magnitude less then the time dura
`tion of the timing pulse on output pin 7 of timer 48.
`Capacitor 62 provides an rf bypass ?lter.
`The trigger pulse from output pin 6 of one shot mono
`stable multivibrator 56 is supplied through resistor 64
`and triggers switch 66, which is provided by a 2N6388
`Darlington connected bipolar transistor pair. The trig
`ger signal base drives transistor 68 into conduction
`which in turn base drives transistor 70 into conduction
`which completes a conductive circuit path from battery
`circuit 22 through current limiting resistor 72 through
`conductive transistor 70 to ground. Base to emitter
`resistors 74 and 76 prevent false triggering of the tran
`sistors, and diode 78 permits reverse inductive dissipa
`tion. A node 80 is provided between the collector of
`transistor 70 and battery circuit 22 and provides an
`input for tachometer 82, which is a Mercury Marine
`Tachometer Part No. 79 19000 A1. The battery circuit
`also includes a power supply provided by a current
`limiting resistor 84, filter capacitors 86 and 88, and a
`voltage regulator 90 provided by a 7805 voltage regula
`tor, providing a 5 volt supply.
`In operation, an ignition pulse on primary lead 28 of
`coil 26 causes output pin 7 of timer 48 to substantially
`immediately transition low. After the noted 1.5 millisec~
`0nd time delay interval, output pin 7 of timer 48 transi
`tions back high. The trailing rising edge of the timing
`pulse from pin 7 of timer 48 causes output pin 6 of one
`shot monostable multivibrator 56 to transition high for
`0.1 milliseconds. The leading rising edge of the trigger
`pulse from output pin 6 of one shot monostable multivi
`brator 56 triggers switch 66 into conduction which
`grounds node 80 through conductive transistor 70. The
`battery circuit voltage at node 80 thus decreases and
`transitions to zero. At the end of the 0.1 millisecond
`trigger interval, the trigger pulse on output pin 6 of one
`
`BRIEF DESCRIPTION OF THE DRAWING
`The sole drawing ?gure is a circuit diagram of a
`tachometer signal conditioning circuit constructed in
`accordance with the invention.
`
`50
`
`DETAILED DESCRIPTION
`There is shown in the drawing a tachometer signal
`conditioning circuit 20 for an internal combustion en
`gine having a battery circuit 22 with a battery 24, and an
`ignition coil 26 with a primary low voltage lead 28 and
`a secondary high voltage lead 30 supplying voltage for
`spark plug 32. The coil is grounded at 34.
`Ignition pulses from primary lead 28 are half wave
`recti?ed by diode 36. Signals below a given threshold
`voltage are blocked by zenner diode 38. The signal
`voltage is then dropped by the voltage divider network
`provided by resistors 40 and 42, and filtered by capaci
`tor 44 and regulated by zener diode 46. The ignition
`pulses are then input to a timer 48 provided by a 2905
`
`55
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`65
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`TOYOTA Ex. 1016, page 3
`Toyota v. Hagenbuch
`IPR2013-00483
`
`

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`4,950,983
`3
`4
`leading edge of said trigger pulse actuating said switch
`shot monostable multivibrator 56 transitions low, thus
`removing the base drive trigger signal from switch 66,
`circuit to said given state, said trailing edge of said
`such that the latter becomes nonconductive and blocks
`trigger pulse actuating said switch circuit to a second
`current ?ow through transistor 70, whereupon the bat
`given state, one of said given states of said switch circuit
`tery circuit voltage at node 80 increases and transitions
`being conductive such that said switch circuit conducts
`back high to a voltage which is less than the battery
`current therethrough from said battery circuit, the
`voltage, as reduced by resistor 72. The conductive and
`other of said given states of said switch circuit being
`nonconductive states of switch 66 change the battery
`nonconductive such that said switch circuit blocks cur
`circuit voltage at node 80 at a frequency corresponding
`rent ?ow therethrough from said battery circuit, to
`to the frequency of ignition pulses on primary lead 28.
`provide a ?rst battery circuit voltage at said node dur
`The voltage at node 80 transitions twice for each igni
`ing said ?rst given state of said switch circuit, and a
`tion pulse. Both transitions occur between successive
`second battery circuit voltage at said node during said
`ignition pulses. After an ignition pulse, the voltage at
`second given state of said switch circuit, and compris
`node 80 transitions low and then back high before the
`ing means for controlling the time duration between
`occurence of the next ignition pulse. The transitions of
`said leading and trailing edges of said trigger pulse
`the voltage level at node 80 provide the tachometer
`according to engine rpm such that both said leading
`input signal for tachometer 82.
`edge and said trailing edge of said trigger pulse occur
`It is recognized that various equivalents, alternatives
`between successive ignition pulses such that following
`and modi?cations are possible within the scope of the
`an ignition pulse said switch circuit transitions to said
`appended claims.'
`‘
`?rst given state and then transitions to said second given
`I claim:
`state before occurence of the next ignition pulse such
`1. A tachometer signal conditioning circuit for an
`that said battery circuit voltage at said node transitions
`internal combustion engine having a battery circuit, and
`from said second battery circuit voltage to said ?rst
`an ignition coil with a primary low voltage lead and a
`battery circuit voltage and then back to said second
`secondary high voltage lead, comprising a timer circuit
`battery circuit voltage between successive ignition
`having an input responsive to ignition pulses from said
`pulses.
`primary lead, and having an output outputting a timing
`4. The invention according to claim 3 wherein said
`pulse terminating after a given time delay interval dur
`switch circuit comprises a transistor which is conduc
`ing which RFI, EMI and other transients on said pri
`tive in said ?rst given state and nonconductive in said
`mary lead are ignored, a one shot monostable multivi
`second given state, such that battery circuit voltage at
`brator circuit having an input responsive to said output
`said node transitions twice for each ignition pulse.
`of said timer circuit, and having an output outputting a
`5. The invention according to claim 4 wherein said
`trigger pulse at the termination of said timing pulse from
`node is between said transistor and said battery circuit,
`said timer circuit after said given time delay interval, a
`and battery circuit voltage at said node decreases in
`switch circuit connected to said battery circuit and
`response to said ?rst given state of said transistor and
`actuated to a given state by said trigger pulse from said
`increases in response to said second given state of said
`one shot monostable multivibrator circuit, said switch
`circuit having a node providing a tachometer input, said
`transistor.
`/
`6. The invention according to claim 4 wherein the
`given state of said switch circuit changing the battery
`time duration between said leading and trailing edges of
`circuit voltage at said node at a frequency correspond
`said timing pulse is an order of magnitude larger then
`ing to the frequency of said ignition pulses.
`the time duration between the leading and trailing edges
`2. The invention according to claim 1 wherein said
`of said trigger pulse.
`timing pulse has a leading edge and a trailing edge, said
`leading edge occuring substantially immediately after
`7. The invention according to claim 4 wherein said
`said ignition pulse, said trailing edge occuring after said
`battery circuit has a battery of a given rated voltage,
`given time delay interval following said leading edge,
`and wherein voltage at said node transitions between
`ground and a voltage which is less than said given rated
`wherein said one shot monostable multivibrator circuit
`input is triggered by said trailing edge of said timing
`voltage, such that said conditioning circuit enables the
`pulse and substantially immediately outputs said trigger
`use of a tachometer rated for voltages less then said
`given rated voltage of said battery, and converts igni
`pulse.
`~
`3. The invention according to claim 2 wherein said
`tion pulses from said coil for use with said tachometer.
`trigger pulse has a leading edge and a trailing edge, said
`
`45
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`50
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`55
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`65
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`20
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`25
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`40
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`TOYOTA Ex. 1016, page 4
`Toyota v. Hagenbuch
`IPR2013-00483