CA1054222A - Timing control circuit for an automotive engine ignition analyzer - Google Patents
Timing control circuit for an automotive engine ignition analyzerInfo
- Publication number
- CA1054222A CA1054222A CA266,554A CA266554A CA1054222A CA 1054222 A CA1054222 A CA 1054222A CA 266554 A CA266554 A CA 266554A CA 1054222 A CA1054222 A CA 1054222A
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- CA
- Canada
- Prior art keywords
- voltage
- engine
- signal
- timing
- circuit
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
- F02P17/00—Testing of ignition installations, e.g. in combination with adjusting; Testing of ignition timing in compression-ignition engines
- F02P17/02—Checking or adjusting ignition timing
- F02P17/04—Checking or adjusting ignition timing dynamically
- F02P17/06—Checking or adjusting ignition timing dynamically using a stroboscopic lamp
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
- F02P17/00—Testing of ignition installations, e.g. in combination with adjusting; Testing of ignition timing in compression-ignition engines
- F02P17/02—Checking or adjusting ignition timing
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R13/00—Arrangements for displaying electric variables or waveforms
- G01R13/20—Cathode-ray oscilloscopes
- G01R13/22—Circuits therefor
- G01R13/24—Time-base deflection circuits
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R13/00—Arrangements for displaying electric variables or waveforms
- G01R13/20—Cathode-ray oscilloscopes
- G01R13/22—Circuits therefor
- G01R13/32—Circuits for displaying non-recurrent functions such as transients; Circuits for triggering; Circuits for synchronisation; Circuits for time-base expansion
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- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Ignition Installations For Internal Combustion Engines (AREA)
- Electrical Control Of Ignition Timing (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
An improved timing control circuit for an automotive en-gine ignition analyzer is disclosed providing an improved sweep signal for the oscilloscope of the analyzer and providing both re-tard and advance lamp triggering signals for driving a strobe lamp associated with the analyzer. The ramp generator incorpor-ated provides self compensation for changes in the engine speed of revolution by employing a phase lock loop with phase detector, in-tegrator and voltage controlled oscillator. The oscillator pro-vides a ramp voltage for use as a sweep signal and input to the strobe lamp signal generator.
The ramp voltage provides a sweep signal of substantially constant length while the engine speed varies over the range of idling to full speed. The timing control por-tion for the strobe lamp used in adjusting the timing of an in-ternal combustion engine provides a signal which retards lamp triggering for setting ignition advance and a signal which ad-vances lamp triggering for setting ignition retard, The circuit provides for advance and retard selection, the amount of advance or retard, and zero degree triggering for engines with various numbers of cylinders. The lamp circuit employs the ramp voltage synchronized with engine timing, a reference voltage for setting the amount of advance or retard, and a comparator which provides a triggering signal for the lamp when the ramp and reference vol-tages match.
An improved timing control circuit for an automotive en-gine ignition analyzer is disclosed providing an improved sweep signal for the oscilloscope of the analyzer and providing both re-tard and advance lamp triggering signals for driving a strobe lamp associated with the analyzer. The ramp generator incorpor-ated provides self compensation for changes in the engine speed of revolution by employing a phase lock loop with phase detector, in-tegrator and voltage controlled oscillator. The oscillator pro-vides a ramp voltage for use as a sweep signal and input to the strobe lamp signal generator.
The ramp voltage provides a sweep signal of substantially constant length while the engine speed varies over the range of idling to full speed. The timing control por-tion for the strobe lamp used in adjusting the timing of an in-ternal combustion engine provides a signal which retards lamp triggering for setting ignition advance and a signal which ad-vances lamp triggering for setting ignition retard, The circuit provides for advance and retard selection, the amount of advance or retard, and zero degree triggering for engines with various numbers of cylinders. The lamp circuit employs the ramp voltage synchronized with engine timing, a reference voltage for setting the amount of advance or retard, and a comparator which provides a triggering signal for the lamp when the ramp and reference vol-tages match.
Description
1054ZZ;~
BACKGROUND OF THE INVENTION
This invention relates to internal combustion engine ig-nition analyzers and in particular, to a new and improved timing circuit for generating sweep signals for the oscilloscope and fir-5. ing signals for the strobe lamp of an analyzer.
Ignition analyzers are utilized at the present time byengine mechanics to provide information regarding the performance of an internal combustion engine, typically the engine for an automobile or truck. A cathode ray oscill~scope is provided for 10. displaying certain types of information, usually with the horizon-tal sweeps being initiated by an ignition timing event such as points closed or No. 1 plug firing or the like. The usual con-stant speed sweep is not satisfactory for engine analyzers where the engine speed will vary over a wide range between idling and 15. full speed. It is desirable to have the horizontal sweep utilize the full width of the tube face regardless of sweep repetition rate, which is proportional to engine speed.
A standard accessory incorporated in the conventional engine analyzer is a strobe or timing lamp which provides a pulse 20. of light of very short duration. In a typical internal combus-tion engine, a fixed reference mark is provided on the engine housing adjacent the flywheel which carries another reference mark. When these two reference marks are aligned, the engine is in the top dead center position which normally corresponds to the 25. firing time for the number 1 cylinder.
The conventional stand-alone strobe lamp is triggered by the number 1 cylinder firing signal during running of the en-gine producing the repeating short light pulse permitting visual determination by the mechanic of the actual engine flywheel posi-30. tion with respect to the fixed reference mark for any enginespeed. Originally, the mechanic noted the difference between the two reference marks, typically in degrees scribed on the 1~354Z~2 flywheel, to determine the amount of advance of number l cylinder firing signal with respect to top dead center.
In improved timing lamps, a variable delay was intro-duced into the timing lamp so that the lamp trigger pulse was de-5. layed with respect to the number l cylinder firing signal. Inusing this improved lamp, the mechanic adjusted the delay so that the two reference marks were aligned when the lamp was triggered and read the calibration of the delay adjustment in terms of de-grees of advance.
lO. This type of device employed a ramp voltage proportional to engine speed which voltage was used as a reference for the de-lay circuit. This simple delay timing circuit has been satisfac-tory for prior engines which were set at some amount of advance.
The present day engines, particularly those equipped 15. with pollution control devices, incorporate both advance and re-tard mechanisms, and some engines are set at a retarded position at idling speed. The simple time delay circuits utilized with the prior art strobe lamps cannot be used for measuring retard settings. That is, the lamps cannot be utilized to advance the 20. lamp firing ahead of the cylinder firing signal.
Prior art ignition analyzer timing circuits have at-tempted to generate a horizontal sweep signal (ramp voltage~ pro-portional to the engine speed and typically utilize amplitude comparison circuits. Various ways have been utilized in the past 25. and each has had some limitation. The limitations on the prior art sweep signal generators usually show up as variation in the sweep length at different engine speeds. It is desirable to have the sweep generating system stable and therefore relatively large time constants are utilized; however, the large time con-30. stants tend to limit the ability of the system to synchronizeitself with rapid changes in engine speed. Attempts have been made to speed up the synchronization by making the circuitry ~054222 under damped. This results in a horizontal trace which at first is too long and then too short before settling down to the proper trace length.
It is an object of the present invention to provide a 5. new and improved timing circuit providing the sweep signal or the oscilloscope of an engine ignition analyzer which provides a horizontal sweep of substantially constant length for a wide range of engine speeds.
A particular object is to provide a phase lock loop for 10. generating the ramp voltage for the sweep signal, making a phase comparison between the engine timing signal and the end of sweep signal, with the slope of the ramp voltage being changed to re-duce any difference in phase of the two signals so that the vol-tage at the end of the ramp (the end of the sweep) remains sub-15. stantially constant regardless of the frequency of the input sig-nals (the sweep repetition rate).
Additionally, it is an object of the present invention to provide a new and improved timing circuit for controlling the firing of a strobe lamp of an engine ignition analyzer.
20. It is a particular object of the invention to provide a new and improved timing circuit providing firing signals for an engine strobe lamp suitable for measuring both advance and retard engine timing.
A further object is to provide such a device which is 25. suitable for use with engines of various numbers of cylinders,and one which can be utilized to provide lamp firlng at the zero degree position as well as advance and retard positions.
SUMMARY OF THE INVENTION
The method of generating the ramp voltage with self-30. compensation for engine speed variations of the invention in-cludes the steps of detecting the occurrence of an engine igni-tion event and providing a reference signal corresponding to the ~1~542Z2 event, generating a ramp voltage for the sweep signal of the oscil-loscope and the strobe lamp firing circuit of the engine ignition analyzer, generating a feedback signal when the ramp voltage reaches a predetermined value, determining the difference in phase between the reference signal and the feedback signal, and varying the slope of the ramp voltage in a direction to decrease this phase difference between the signals.
The invention includes a method of retarding and advanc-ing the triggering of a strobe lamp with respect to the top dead 10. center timing of an engine for providing advance and retard en-gine settings including in addition to the aforementioned steps of detecting the occurrence of engîne ignition timing events and generating a synchronized voltage, the steps of inverting the ramp voltage synchronized with the engine timing, generating a 15. reference voltage which varies as a function of the desired devia-tion of lamp triggering from top dead center, selecting one of the ramp and inverted ramp voltages depending on whether the lamp triggering is to be retarded or advanced, and triggering the strobe lamp when the selected voltage and the reference voltage 20. are matched.
The apparatus comprising the timing circuit of the in-vention comprises a ramp voltage generator for the oscilloscope and strobe lamp firing circuit of an engine ignition analyzer including a pickup responsive to the engine ignition timing for 25. generating a first electrical signal, a phase lock loop with phase detector, integrator, and voltage controlled oscillator, a comparator circuit having a reference voltage and the output of the oscillator as inputs and providing a feedback signal when the oscillator output reaches a predetermined value, with the 30. first signal and the feedback signal connected to the phase de-tector as inputs. The phase detector output provides an input to the integrator which in turn provides an input to the ` 1054Z2Z
o~cillator, with the output o the oscillator being the desired ramp voltage.
The invention al80 includes for the timing control circuit for such a strobe lamp circuitry responsive to the ramp voltage synchronized with the engine ignition timing and having the ramp as an input thereto, circuitry for producing the reference voltage including means for varying the reference voltage as a function of the desired amount of deviation, a comparator having the ramp and reference voltages as inputs and providing an output for use as a trigger voltage when the ramp voltage matches the reference voltage. The circuit further includes an inverter for producing an inverted ramp voltage, and an advance-re~ard selection switch for selecting one of the ramp and inverted ramp voltages as an input to the comparator.
Thus ~ the present invention discloses a timing control circuit for an engine ignition analyzer including an oscilloscope and a strobe lamp for use in the adjustment of an internal combustion engine having a fixed reference mark and a moving reference mark with an engine adjustment reference point occurring when the reference marks are aligned, this timing control circuit including a means for producing an increasing ramp voltage synchronized with the engine ignition timing, a means for producing a decreasing ramp voltage synchroniæed with the engine ignition timing, a means for producing a reference voltage including means for varying the reference voltage as a function of the desired amount of deviation of lamp flash from the incurrence of the engine ad~ustment reference point, a comparator having flrst and 3econd input terminals and providing an output pulse when a positive going voltage applied to the first terminal equals a reference voltage applied to the second terminal and when the negatlve going voltage applied to the second terminal ~054ZZZ -equals a reference voltage applied to the first terminal, a first switch means for connecting the increasing ramp voltage and the reference voltage to the first and second terminals respectively of the comparator when in a first position and connecting the decrePsing ramp voltage and the reference voltage to the first and second terminals respectively when in a second position whereby advance or retard deviation of lamp flash can be selected, a means for connecting the comparator output to the strQbe lamp as a trigger voltage, ;10 and means for connecting the increasing ramp voltage to the oscilloscope as the sweep voltage. The present invention also discloses a method of retarding and advancing the triggering of a strobe lamp and sweeping the oscilloscope of an engine ignition analyzer with respect to an adjustment reference point of an engine which includes the steps of detecting the occurrence of engine ignition timing events, generating an increasing lamp voltage and a decreasing lamp voltage synchronized with the engine ignition timing, trigger-ing the oscilloscope sweep with the increasing ramp voltage, generating a reference voltage of a magnitude varying as a function of the desired strobe lamp triggering deviation from the ad~ustment reference point, selecting one of the increas-ing ramp and ramp voltages depending on whether the strobe lamp triggering is to be retarded or advanced, and trigger-ing the strobe lamp when the selected voltage and reference voltage are matched.
DESCRIPTION OF THE DRAWINGS
Figo 1 is a block diagram showing an engine ignition analyzer incorporating the presently preferred embodiment of the ramp generator of the invention;
Fig. 2 i~ an electrical schemstic of the sweep generator of Fig. l;
Fig. 3 is a circuit slmilar to that of Fig~ 2 showing ~ (~OQ, mb/C'~
~054ZZZ
an alternative embodlment of the sweep generator; and Fig. 4 is an electrlcal diagram of the strobe lamp control portion of the present invention incorporatlng the preferred embodiment of the ramp generator.
DESCRIPTION OF THR PREFERRED EMBODIMENTS
The ignltion analyzer illustrated in Fig. 1 includes a pickup 10, a sweep generator 11 and an oscilloscope 12.
The pickup provides an electrical output signal in the form of a train of pulses 15, which pulses are related in time to some event in the engine ignition system, such as points open or points closed or No. 1 plug firing or the like.
~b/C~ . - 6b -The pickup is coupled to some point in the ignition sys-tem by direct coupling or by inductive coupling or by capacitive coupling as desired, and the pickup may be of conventional design.
5. The sweep generator 11 provides the horizontal sweep signal for the trace of the oscilloscope 12 in the form of a cyc-lically repeating ramp voltage 16. The sweep signal is connected to the horizontal deflection plates of the oscilloscope in the conventional manner, and the signal to be displayed is connected 10. to the vertical deflection plate. Sweep generator 11 also pro-vides the input to the strobe lamp driving portion of the circuit to be described hereinafter in detail.
The time interval between pulses 15 varies with the speed of the engine. The function of the sweep generator is to 15. provide the ramp voltage 16 with a substantially constant peak value so that the sweep width is substantially the same regard-less of the sweep rate or interval between sweep initiation sig-nals (i.e., regaxdless of engine speed). This is accomplished by utilizing a phase lock loop in the sweep generator with phase de-20. tector 20, integrator 21 and voltage control oscillator 22. Thepresently preferred embodiment for the sweep generator is shown in Fig. 2.
The phase detector 20 includes flip-flops A and B. The pulses 15 (designated Fref) are connected as the input of flip-25. flop A. The input to flip-flop B is another train of pulses 25 (designated Ffb). The pulses 25 are produced by a comparator 26 when the ramp voltage Er reaches a predetermined value, as deter-mined by a reference voltage input Vref to the comparator 26.
In the system as illustrated, the flip-flop A is set 30~ by the positive going edge of a pulse 15 and the flip-flop B is set by the positive going edge of a pulse 25. The flip-flops are reset by a reset circuit including gates 28, 29 which provide ~5~;~Z~
the reset voltage when both flip-flops are set. The signal on line 30 is normally high and goes negative upon the occurrence of the engine ignition timing event with which the beginning of the ramp 16 is synchronized. Gate 29 acts as an OR gate and will re-5. set flip-flops A and B either when both A and B are in the set state or upon the occurrence of the negative going portion of the signal on line 30. This later signal assures that both flip-flops A and B are in the normal or reset state at the beginning of the ramp and prevents the system from getting out of 10. synchronization.
Resistors Rl and R2 are connected as a voltage divider with the junction D connected as the input to the integrator 21 through resistor R3. When flip-flop A is in the normal or reset state, resistor Rl is tied to a known voltage (in this case, 0).
15. Similarly, when flip-flop B is in the normal state, resistor R2 is tied to a known voltage (designated as V). Amplifier ARl of the integrator 21 has its reference input tied to voltage V0 which is set to be equal to the potential at the junction D when both flip-flops are in the reset state (in this example, V/2).
20. Under this condition, there is no current through the resistor R3 and the integrator output Eo does not change. When only one of the flip-flops is set, the potential at D is greater than or less than the potential V0 by a step function amount V/2 produc-ing a current in the resistor R3 and a change in the integrator 25. output Eo as will be hereinafter described in greater detail.
The amplifier AR2 of the voltage controlled oscillator 22 provides the output E4 in the form of a ramp the slope of which is propor~ional to Eo~ When the voltage Er reaches a value equal to Vref, the pulse 25 is generated by the comparator 26.
30. If the Fref pulse 15 occurs before the Ffb pulse 25, flip-flop A
is set and resistor Rl is connected to the voltage (V) causing point D to go from a potential of V/2 to V and the output Eo to ~)S4Z22 move in a negative direction. This causes the ramp Er to change slope and reach Vref sooner than it did in the preceding cycle.
After the pulse 25 is generated, flip-flop s is set also and then both flip-flops are reset causing point D to once again 5. assure a potential of V/2 and output Eo to stabilize at its achieved value. If the Fref pulse occurs after the Ffb pulse, the reverse operation occurs with point D going from a potential of V/2 to 0 and the output Eo moving in a positive direction.
This causes the ramp Er to reach Vref later than it did in the 10. preceding cycle. With this pulsed compensation arrangement, the length of the horizontal sweep is controlled by Vref and is not subject to voltage or current feedback from a tachometer circuit or other variable related to engine speed.
The voltage controlled oscillator is reset to the ini-15. tial condition by a switching transistor 33 connected across the output and input of amplifier AR2. The transistor 33 is actuated to the conducting condition by the negative going signal at 30 through a one shot multivibrator 34. In an alternative embodi-ment shown in Fig. 3, resetting is accomplished by using the sig-20. nal Ffb for controlling the switching transistor 33. The signalat 30 may be omitted entirely, with the flip-flops being reset by gate 28 when both flip-flops are in the set state.
The time duration of t of the sweep is t =
25. where dv is the maximum voltage of the ramp (as determined by Vref). The transfer function of the integrator is Eo 1 + j~T2 Ein j (1)~1 where ~1 = [(Rl or R2) + R3]Cl l2 = R4 Cl ~os4222 The phase lock loop functions to reduce the phase dif-ference between the inputs to the two flip-flops to a minimum and thereby maintain the maximum voltage of the ramp substantially constant so that the length of the sweep will be substantially 5. constant and independent of the input pulse rates at the flip-flops (i.e., engine speed).
Referring now to Fig. 4, the strobe lamp firing portion of the circuit includes an inverter 120, a selection switch 121, and a comparator 122. The ramp voltage 16 is connected to one 10. fixed terminal (A) of one contact set of the advance-retard se-lection switch 121, and as an input to the inverter 120 through a resistor 123, with the inverter input connected to a negative voltage source through a variable resistor 124 which provides a zero adjustment. The inverter output is an inverted ramp voltage 15. 127 which is connected to a fixed terminal (R) of another contact set of the switch 121.
A reference voltage is connected to a fixed terminal (R) of the first contact set of the switch 121 and to a fixed terminal (A) of the second contact set. In the embodiment illustrated, the 20. reference voltage is provided by an amplifier 130, a control po-tentiometer 131 and another amplifier 132 to form a positive vol-tage source. The potentiometer 131 provides for variation of the reference voltage by the mechanic or other person utilizing the strobe lamp. The amplifier 130 provides isolation of the control 25. potentiometer from the voltage source and the amplifier 132 pro-vides inversion of the reference voltage and isolation. A poten-tiometer 133 is connected across positive and negative voltage sources, with the moving arm connected to the input of amplifier 132 to provide a bias for the advance zero adjustment.
30. The moving terminals of the first and second contact sets of the switch 121 are connected to the inputs of the com-parator 122 through resistors 136 and diodes 137 which protect los42~2 the input from large differential voltages. In the embodiment illustrated, the output of the comparator is a negative going step 140 generated when the negative input matches the positive input. When the switch 121 is in the position illustrated, con 5. necting the A terminals as inputs, the circuit is in the advance mode and the comparator output is generated when the rising vol-tage of the ramp 16 matches the level of the reference voltage.
With the switch in the opposite or retard position connecting the R terminals as comparator inputs, the comparator output step 140 10. is generated when the falling voltage of the ramp 127 reaches the level of the reference voltage.
The comparator output 140 provides the triggering sig-nal for the lamp 145, preferably through a one shot multivibrator 146 and an OR circuit 147. The negative going step 140 is con-15. nected to the one shot 146 through a capacitor 148, with the oneshot providing a voltage pulse 149 as an output. The OR circuit 147 connects either the voltage pulse 149 or a voltage pulse 150 as the trigger pulse to the lamp 145, depending on the setting of switch 151. With the switch 151 in the open position as 20. shown in Fig. 4, the pulse 150 provides the triggering. With the switch 151 closed, the pulse 149 provides the triggering.
Typically the pulse 150 is generated in the engine analyzer and corresponds in time to the firing signal for the number 1 cylin-der, that is, top dead center for the engine which is zero de-25. grees advance and retard. The switch 151 preferably is mountedwith the potentiometer 131 so that when the operator sets the desired deviation (advance or retard) at or close to zero de-grees, the switch 151 is closed. This provides direct control of the timing lamp from the engine timing signals without advance 30. or retard from the timing control circuit.
The reference voltage is also connected as an input to a meter 160 through a gain adjustment resistor 161 and amplifier ~o542ZZ
162. The meter may be calibrated to read directly in degrees of advance or retard. A plurality of gain control circuits 163 are connected across the amplifier 162, each comprising a resistor and switch in series. The appropriate switch is closed, depend-5. ing on whether the engine under test is a four, six or eight cyl-inder reciprocating engine or a rotary engine, to provide the appropriate gain for the meter 160.
Ordinarily the timing lamp 145 would be fired for each ramp of the sweep generator output. When there is a ramp for 10. each cylinder firing, this would produce excessive lamp firing, since in ordinary engines, the moving reference mark appears ad-jacent the fi~ed reference mark only at the time of firing of num-ber 1 cylinder. An inhibit circuit 166 is provided for inhibit-ing lamp firing except at the time of number 1 cylinder firing.
15. The inhibit circuit includes an OR circuit 167 having as one in-put a pulse 169 which is true from the firing time of number 1 cylinder to the firing time of number 2 cylinder, and another pulse 168 which is true from the firing time of cylinder N pre-ceding number 1 cylinder to the firing time of number 1 cylinder.
20. While cylinders are referred to herein, the system is equally usable with rotary engines, where the number of rotors usually corresponds to the number of cylinders in a reciprocating engine.
Another contact set of the advance-retard selection switch 121 provides inputs to the OR circuit 167 so that the one shot multi-25. vibrator 146 is inhibited except during the number 1 pulse 169when engine advance setting is desired, or during number N pulse 168 when engine retard setting is desired.
In operation, the potentiometer 131 may initially be set at the zero degrees position with the switch 151 closed and 30. with the switch 121 in the advance position. Then the timing lamp is fired by the number 1 cylinder pulse and the engine con-dition may be determined by visually observing the distance 105~Z;~:2 between the reference marks. When the reference marks are a-ligned, the timing deviation is zero degrees.
If the potentiometer 131 is moved to a new setting, say three degrees, and one of the switches 163 is closed, say the 5. eight cylinder switch, the meter 160 will indicate three degrees.
The comparator will provide the negative step output 140 when the magnitude of the ramp 16 rises to the magnitude of the reference voltage, which delays the firing of the lamp 145 a period of time corresponding to three degrees of flywheel rotation. If the se-10. lection switch 121 is moved to the retard position, the compara-tor output will be provided when the inverted ramp for cylinder N
falls to the magnitude of the reference voltage with the result that the timing lamp is fired prior to the firing of the number 1 cylinder by the desired three degrees.
15. While specific polarities have been used in the preced-ing description, it will be readily understood that the invention is not so limited and that different polarities may be used as desired.
BACKGROUND OF THE INVENTION
This invention relates to internal combustion engine ig-nition analyzers and in particular, to a new and improved timing circuit for generating sweep signals for the oscilloscope and fir-5. ing signals for the strobe lamp of an analyzer.
Ignition analyzers are utilized at the present time byengine mechanics to provide information regarding the performance of an internal combustion engine, typically the engine for an automobile or truck. A cathode ray oscill~scope is provided for 10. displaying certain types of information, usually with the horizon-tal sweeps being initiated by an ignition timing event such as points closed or No. 1 plug firing or the like. The usual con-stant speed sweep is not satisfactory for engine analyzers where the engine speed will vary over a wide range between idling and 15. full speed. It is desirable to have the horizontal sweep utilize the full width of the tube face regardless of sweep repetition rate, which is proportional to engine speed.
A standard accessory incorporated in the conventional engine analyzer is a strobe or timing lamp which provides a pulse 20. of light of very short duration. In a typical internal combus-tion engine, a fixed reference mark is provided on the engine housing adjacent the flywheel which carries another reference mark. When these two reference marks are aligned, the engine is in the top dead center position which normally corresponds to the 25. firing time for the number 1 cylinder.
The conventional stand-alone strobe lamp is triggered by the number 1 cylinder firing signal during running of the en-gine producing the repeating short light pulse permitting visual determination by the mechanic of the actual engine flywheel posi-30. tion with respect to the fixed reference mark for any enginespeed. Originally, the mechanic noted the difference between the two reference marks, typically in degrees scribed on the 1~354Z~2 flywheel, to determine the amount of advance of number l cylinder firing signal with respect to top dead center.
In improved timing lamps, a variable delay was intro-duced into the timing lamp so that the lamp trigger pulse was de-5. layed with respect to the number l cylinder firing signal. Inusing this improved lamp, the mechanic adjusted the delay so that the two reference marks were aligned when the lamp was triggered and read the calibration of the delay adjustment in terms of de-grees of advance.
lO. This type of device employed a ramp voltage proportional to engine speed which voltage was used as a reference for the de-lay circuit. This simple delay timing circuit has been satisfac-tory for prior engines which were set at some amount of advance.
The present day engines, particularly those equipped 15. with pollution control devices, incorporate both advance and re-tard mechanisms, and some engines are set at a retarded position at idling speed. The simple time delay circuits utilized with the prior art strobe lamps cannot be used for measuring retard settings. That is, the lamps cannot be utilized to advance the 20. lamp firing ahead of the cylinder firing signal.
Prior art ignition analyzer timing circuits have at-tempted to generate a horizontal sweep signal (ramp voltage~ pro-portional to the engine speed and typically utilize amplitude comparison circuits. Various ways have been utilized in the past 25. and each has had some limitation. The limitations on the prior art sweep signal generators usually show up as variation in the sweep length at different engine speeds. It is desirable to have the sweep generating system stable and therefore relatively large time constants are utilized; however, the large time con-30. stants tend to limit the ability of the system to synchronizeitself with rapid changes in engine speed. Attempts have been made to speed up the synchronization by making the circuitry ~054222 under damped. This results in a horizontal trace which at first is too long and then too short before settling down to the proper trace length.
It is an object of the present invention to provide a 5. new and improved timing circuit providing the sweep signal or the oscilloscope of an engine ignition analyzer which provides a horizontal sweep of substantially constant length for a wide range of engine speeds.
A particular object is to provide a phase lock loop for 10. generating the ramp voltage for the sweep signal, making a phase comparison between the engine timing signal and the end of sweep signal, with the slope of the ramp voltage being changed to re-duce any difference in phase of the two signals so that the vol-tage at the end of the ramp (the end of the sweep) remains sub-15. stantially constant regardless of the frequency of the input sig-nals (the sweep repetition rate).
Additionally, it is an object of the present invention to provide a new and improved timing circuit for controlling the firing of a strobe lamp of an engine ignition analyzer.
20. It is a particular object of the invention to provide a new and improved timing circuit providing firing signals for an engine strobe lamp suitable for measuring both advance and retard engine timing.
A further object is to provide such a device which is 25. suitable for use with engines of various numbers of cylinders,and one which can be utilized to provide lamp firlng at the zero degree position as well as advance and retard positions.
SUMMARY OF THE INVENTION
The method of generating the ramp voltage with self-30. compensation for engine speed variations of the invention in-cludes the steps of detecting the occurrence of an engine igni-tion event and providing a reference signal corresponding to the ~1~542Z2 event, generating a ramp voltage for the sweep signal of the oscil-loscope and the strobe lamp firing circuit of the engine ignition analyzer, generating a feedback signal when the ramp voltage reaches a predetermined value, determining the difference in phase between the reference signal and the feedback signal, and varying the slope of the ramp voltage in a direction to decrease this phase difference between the signals.
The invention includes a method of retarding and advanc-ing the triggering of a strobe lamp with respect to the top dead 10. center timing of an engine for providing advance and retard en-gine settings including in addition to the aforementioned steps of detecting the occurrence of engîne ignition timing events and generating a synchronized voltage, the steps of inverting the ramp voltage synchronized with the engine timing, generating a 15. reference voltage which varies as a function of the desired devia-tion of lamp triggering from top dead center, selecting one of the ramp and inverted ramp voltages depending on whether the lamp triggering is to be retarded or advanced, and triggering the strobe lamp when the selected voltage and the reference voltage 20. are matched.
The apparatus comprising the timing circuit of the in-vention comprises a ramp voltage generator for the oscilloscope and strobe lamp firing circuit of an engine ignition analyzer including a pickup responsive to the engine ignition timing for 25. generating a first electrical signal, a phase lock loop with phase detector, integrator, and voltage controlled oscillator, a comparator circuit having a reference voltage and the output of the oscillator as inputs and providing a feedback signal when the oscillator output reaches a predetermined value, with the 30. first signal and the feedback signal connected to the phase de-tector as inputs. The phase detector output provides an input to the integrator which in turn provides an input to the ` 1054Z2Z
o~cillator, with the output o the oscillator being the desired ramp voltage.
The invention al80 includes for the timing control circuit for such a strobe lamp circuitry responsive to the ramp voltage synchronized with the engine ignition timing and having the ramp as an input thereto, circuitry for producing the reference voltage including means for varying the reference voltage as a function of the desired amount of deviation, a comparator having the ramp and reference voltages as inputs and providing an output for use as a trigger voltage when the ramp voltage matches the reference voltage. The circuit further includes an inverter for producing an inverted ramp voltage, and an advance-re~ard selection switch for selecting one of the ramp and inverted ramp voltages as an input to the comparator.
Thus ~ the present invention discloses a timing control circuit for an engine ignition analyzer including an oscilloscope and a strobe lamp for use in the adjustment of an internal combustion engine having a fixed reference mark and a moving reference mark with an engine adjustment reference point occurring when the reference marks are aligned, this timing control circuit including a means for producing an increasing ramp voltage synchronized with the engine ignition timing, a means for producing a decreasing ramp voltage synchroniæed with the engine ignition timing, a means for producing a reference voltage including means for varying the reference voltage as a function of the desired amount of deviation of lamp flash from the incurrence of the engine ad~ustment reference point, a comparator having flrst and 3econd input terminals and providing an output pulse when a positive going voltage applied to the first terminal equals a reference voltage applied to the second terminal and when the negatlve going voltage applied to the second terminal ~054ZZZ -equals a reference voltage applied to the first terminal, a first switch means for connecting the increasing ramp voltage and the reference voltage to the first and second terminals respectively of the comparator when in a first position and connecting the decrePsing ramp voltage and the reference voltage to the first and second terminals respectively when in a second position whereby advance or retard deviation of lamp flash can be selected, a means for connecting the comparator output to the strQbe lamp as a trigger voltage, ;10 and means for connecting the increasing ramp voltage to the oscilloscope as the sweep voltage. The present invention also discloses a method of retarding and advancing the triggering of a strobe lamp and sweeping the oscilloscope of an engine ignition analyzer with respect to an adjustment reference point of an engine which includes the steps of detecting the occurrence of engine ignition timing events, generating an increasing lamp voltage and a decreasing lamp voltage synchronized with the engine ignition timing, trigger-ing the oscilloscope sweep with the increasing ramp voltage, generating a reference voltage of a magnitude varying as a function of the desired strobe lamp triggering deviation from the ad~ustment reference point, selecting one of the increas-ing ramp and ramp voltages depending on whether the strobe lamp triggering is to be retarded or advanced, and trigger-ing the strobe lamp when the selected voltage and reference voltage are matched.
DESCRIPTION OF THE DRAWINGS
Figo 1 is a block diagram showing an engine ignition analyzer incorporating the presently preferred embodiment of the ramp generator of the invention;
Fig. 2 i~ an electrical schemstic of the sweep generator of Fig. l;
Fig. 3 is a circuit slmilar to that of Fig~ 2 showing ~ (~OQ, mb/C'~
~054ZZZ
an alternative embodlment of the sweep generator; and Fig. 4 is an electrlcal diagram of the strobe lamp control portion of the present invention incorporatlng the preferred embodiment of the ramp generator.
DESCRIPTION OF THR PREFERRED EMBODIMENTS
The ignltion analyzer illustrated in Fig. 1 includes a pickup 10, a sweep generator 11 and an oscilloscope 12.
The pickup provides an electrical output signal in the form of a train of pulses 15, which pulses are related in time to some event in the engine ignition system, such as points open or points closed or No. 1 plug firing or the like.
~b/C~ . - 6b -The pickup is coupled to some point in the ignition sys-tem by direct coupling or by inductive coupling or by capacitive coupling as desired, and the pickup may be of conventional design.
5. The sweep generator 11 provides the horizontal sweep signal for the trace of the oscilloscope 12 in the form of a cyc-lically repeating ramp voltage 16. The sweep signal is connected to the horizontal deflection plates of the oscilloscope in the conventional manner, and the signal to be displayed is connected 10. to the vertical deflection plate. Sweep generator 11 also pro-vides the input to the strobe lamp driving portion of the circuit to be described hereinafter in detail.
The time interval between pulses 15 varies with the speed of the engine. The function of the sweep generator is to 15. provide the ramp voltage 16 with a substantially constant peak value so that the sweep width is substantially the same regard-less of the sweep rate or interval between sweep initiation sig-nals (i.e., regaxdless of engine speed). This is accomplished by utilizing a phase lock loop in the sweep generator with phase de-20. tector 20, integrator 21 and voltage control oscillator 22. Thepresently preferred embodiment for the sweep generator is shown in Fig. 2.
The phase detector 20 includes flip-flops A and B. The pulses 15 (designated Fref) are connected as the input of flip-25. flop A. The input to flip-flop B is another train of pulses 25 (designated Ffb). The pulses 25 are produced by a comparator 26 when the ramp voltage Er reaches a predetermined value, as deter-mined by a reference voltage input Vref to the comparator 26.
In the system as illustrated, the flip-flop A is set 30~ by the positive going edge of a pulse 15 and the flip-flop B is set by the positive going edge of a pulse 25. The flip-flops are reset by a reset circuit including gates 28, 29 which provide ~5~;~Z~
the reset voltage when both flip-flops are set. The signal on line 30 is normally high and goes negative upon the occurrence of the engine ignition timing event with which the beginning of the ramp 16 is synchronized. Gate 29 acts as an OR gate and will re-5. set flip-flops A and B either when both A and B are in the set state or upon the occurrence of the negative going portion of the signal on line 30. This later signal assures that both flip-flops A and B are in the normal or reset state at the beginning of the ramp and prevents the system from getting out of 10. synchronization.
Resistors Rl and R2 are connected as a voltage divider with the junction D connected as the input to the integrator 21 through resistor R3. When flip-flop A is in the normal or reset state, resistor Rl is tied to a known voltage (in this case, 0).
15. Similarly, when flip-flop B is in the normal state, resistor R2 is tied to a known voltage (designated as V). Amplifier ARl of the integrator 21 has its reference input tied to voltage V0 which is set to be equal to the potential at the junction D when both flip-flops are in the reset state (in this example, V/2).
20. Under this condition, there is no current through the resistor R3 and the integrator output Eo does not change. When only one of the flip-flops is set, the potential at D is greater than or less than the potential V0 by a step function amount V/2 produc-ing a current in the resistor R3 and a change in the integrator 25. output Eo as will be hereinafter described in greater detail.
The amplifier AR2 of the voltage controlled oscillator 22 provides the output E4 in the form of a ramp the slope of which is propor~ional to Eo~ When the voltage Er reaches a value equal to Vref, the pulse 25 is generated by the comparator 26.
30. If the Fref pulse 15 occurs before the Ffb pulse 25, flip-flop A
is set and resistor Rl is connected to the voltage (V) causing point D to go from a potential of V/2 to V and the output Eo to ~)S4Z22 move in a negative direction. This causes the ramp Er to change slope and reach Vref sooner than it did in the preceding cycle.
After the pulse 25 is generated, flip-flop s is set also and then both flip-flops are reset causing point D to once again 5. assure a potential of V/2 and output Eo to stabilize at its achieved value. If the Fref pulse occurs after the Ffb pulse, the reverse operation occurs with point D going from a potential of V/2 to 0 and the output Eo moving in a positive direction.
This causes the ramp Er to reach Vref later than it did in the 10. preceding cycle. With this pulsed compensation arrangement, the length of the horizontal sweep is controlled by Vref and is not subject to voltage or current feedback from a tachometer circuit or other variable related to engine speed.
The voltage controlled oscillator is reset to the ini-15. tial condition by a switching transistor 33 connected across the output and input of amplifier AR2. The transistor 33 is actuated to the conducting condition by the negative going signal at 30 through a one shot multivibrator 34. In an alternative embodi-ment shown in Fig. 3, resetting is accomplished by using the sig-20. nal Ffb for controlling the switching transistor 33. The signalat 30 may be omitted entirely, with the flip-flops being reset by gate 28 when both flip-flops are in the set state.
The time duration of t of the sweep is t =
25. where dv is the maximum voltage of the ramp (as determined by Vref). The transfer function of the integrator is Eo 1 + j~T2 Ein j (1)~1 where ~1 = [(Rl or R2) + R3]Cl l2 = R4 Cl ~os4222 The phase lock loop functions to reduce the phase dif-ference between the inputs to the two flip-flops to a minimum and thereby maintain the maximum voltage of the ramp substantially constant so that the length of the sweep will be substantially 5. constant and independent of the input pulse rates at the flip-flops (i.e., engine speed).
Referring now to Fig. 4, the strobe lamp firing portion of the circuit includes an inverter 120, a selection switch 121, and a comparator 122. The ramp voltage 16 is connected to one 10. fixed terminal (A) of one contact set of the advance-retard se-lection switch 121, and as an input to the inverter 120 through a resistor 123, with the inverter input connected to a negative voltage source through a variable resistor 124 which provides a zero adjustment. The inverter output is an inverted ramp voltage 15. 127 which is connected to a fixed terminal (R) of another contact set of the switch 121.
A reference voltage is connected to a fixed terminal (R) of the first contact set of the switch 121 and to a fixed terminal (A) of the second contact set. In the embodiment illustrated, the 20. reference voltage is provided by an amplifier 130, a control po-tentiometer 131 and another amplifier 132 to form a positive vol-tage source. The potentiometer 131 provides for variation of the reference voltage by the mechanic or other person utilizing the strobe lamp. The amplifier 130 provides isolation of the control 25. potentiometer from the voltage source and the amplifier 132 pro-vides inversion of the reference voltage and isolation. A poten-tiometer 133 is connected across positive and negative voltage sources, with the moving arm connected to the input of amplifier 132 to provide a bias for the advance zero adjustment.
30. The moving terminals of the first and second contact sets of the switch 121 are connected to the inputs of the com-parator 122 through resistors 136 and diodes 137 which protect los42~2 the input from large differential voltages. In the embodiment illustrated, the output of the comparator is a negative going step 140 generated when the negative input matches the positive input. When the switch 121 is in the position illustrated, con 5. necting the A terminals as inputs, the circuit is in the advance mode and the comparator output is generated when the rising vol-tage of the ramp 16 matches the level of the reference voltage.
With the switch in the opposite or retard position connecting the R terminals as comparator inputs, the comparator output step 140 10. is generated when the falling voltage of the ramp 127 reaches the level of the reference voltage.
The comparator output 140 provides the triggering sig-nal for the lamp 145, preferably through a one shot multivibrator 146 and an OR circuit 147. The negative going step 140 is con-15. nected to the one shot 146 through a capacitor 148, with the oneshot providing a voltage pulse 149 as an output. The OR circuit 147 connects either the voltage pulse 149 or a voltage pulse 150 as the trigger pulse to the lamp 145, depending on the setting of switch 151. With the switch 151 in the open position as 20. shown in Fig. 4, the pulse 150 provides the triggering. With the switch 151 closed, the pulse 149 provides the triggering.
Typically the pulse 150 is generated in the engine analyzer and corresponds in time to the firing signal for the number 1 cylin-der, that is, top dead center for the engine which is zero de-25. grees advance and retard. The switch 151 preferably is mountedwith the potentiometer 131 so that when the operator sets the desired deviation (advance or retard) at or close to zero de-grees, the switch 151 is closed. This provides direct control of the timing lamp from the engine timing signals without advance 30. or retard from the timing control circuit.
The reference voltage is also connected as an input to a meter 160 through a gain adjustment resistor 161 and amplifier ~o542ZZ
162. The meter may be calibrated to read directly in degrees of advance or retard. A plurality of gain control circuits 163 are connected across the amplifier 162, each comprising a resistor and switch in series. The appropriate switch is closed, depend-5. ing on whether the engine under test is a four, six or eight cyl-inder reciprocating engine or a rotary engine, to provide the appropriate gain for the meter 160.
Ordinarily the timing lamp 145 would be fired for each ramp of the sweep generator output. When there is a ramp for 10. each cylinder firing, this would produce excessive lamp firing, since in ordinary engines, the moving reference mark appears ad-jacent the fi~ed reference mark only at the time of firing of num-ber 1 cylinder. An inhibit circuit 166 is provided for inhibit-ing lamp firing except at the time of number 1 cylinder firing.
15. The inhibit circuit includes an OR circuit 167 having as one in-put a pulse 169 which is true from the firing time of number 1 cylinder to the firing time of number 2 cylinder, and another pulse 168 which is true from the firing time of cylinder N pre-ceding number 1 cylinder to the firing time of number 1 cylinder.
20. While cylinders are referred to herein, the system is equally usable with rotary engines, where the number of rotors usually corresponds to the number of cylinders in a reciprocating engine.
Another contact set of the advance-retard selection switch 121 provides inputs to the OR circuit 167 so that the one shot multi-25. vibrator 146 is inhibited except during the number 1 pulse 169when engine advance setting is desired, or during number N pulse 168 when engine retard setting is desired.
In operation, the potentiometer 131 may initially be set at the zero degrees position with the switch 151 closed and 30. with the switch 121 in the advance position. Then the timing lamp is fired by the number 1 cylinder pulse and the engine con-dition may be determined by visually observing the distance 105~Z;~:2 between the reference marks. When the reference marks are a-ligned, the timing deviation is zero degrees.
If the potentiometer 131 is moved to a new setting, say three degrees, and one of the switches 163 is closed, say the 5. eight cylinder switch, the meter 160 will indicate three degrees.
The comparator will provide the negative step output 140 when the magnitude of the ramp 16 rises to the magnitude of the reference voltage, which delays the firing of the lamp 145 a period of time corresponding to three degrees of flywheel rotation. If the se-10. lection switch 121 is moved to the retard position, the compara-tor output will be provided when the inverted ramp for cylinder N
falls to the magnitude of the reference voltage with the result that the timing lamp is fired prior to the firing of the number 1 cylinder by the desired three degrees.
15. While specific polarities have been used in the preced-ing description, it will be readily understood that the invention is not so limited and that different polarities may be used as desired.
Claims (28)
1. A timing control circuit for an engine ignition analyzer including an oscilloscope and a strobe lamp for use in the adjustment of an internal combustion engine having a fixed reference mark and a moving reference mark with an engine adjust-ment reference point occurring when said reference marks are aligned, comprising:
means for producing an increasing ramp voltage synchro-nized with the engine ignition timing;
means for producing a decreasing ramp voltage synchro-nized with the engine ignition timing;
means for producing a reference voltage including means for varying said reference voltage as a function of the desired amount of deviation of lamp flash from the occurrence of the en-gine adjustment reference point;
a comparator having first and second input terminals and providing an output pulse when a positive going voltage applied to said first terminal equals a reference voltage applied to said second terminal and when a negative going voltage applied to said second terminal equals a reference voltage applied to said first terminal;
first switch means for connecting said increasing ramp voltage and said reference voltage to said first and second ter-minals respectively of said comparator when in a first position and connecting said decreasing ramp voltage and said reference voltage to said second and first terminals respectively when in a second position whereby advance or retard deviation of lamp flash can be selected;
means for connecting said comparator output to the strobe lamp as a trigger voltage; and, means for connecting said increasing ramp voltage to the oscilloscope as the sweep voltage.
means for producing an increasing ramp voltage synchro-nized with the engine ignition timing;
means for producing a decreasing ramp voltage synchro-nized with the engine ignition timing;
means for producing a reference voltage including means for varying said reference voltage as a function of the desired amount of deviation of lamp flash from the occurrence of the en-gine adjustment reference point;
a comparator having first and second input terminals and providing an output pulse when a positive going voltage applied to said first terminal equals a reference voltage applied to said second terminal and when a negative going voltage applied to said second terminal equals a reference voltage applied to said first terminal;
first switch means for connecting said increasing ramp voltage and said reference voltage to said first and second ter-minals respectively of said comparator when in a first position and connecting said decreasing ramp voltage and said reference voltage to said second and first terminals respectively when in a second position whereby advance or retard deviation of lamp flash can be selected;
means for connecting said comparator output to the strobe lamp as a trigger voltage; and, means for connecting said increasing ramp voltage to the oscilloscope as the sweep voltage.
2. A timing control circuit as defined in claim 1 including:
a deviation indicating meter; and means for connecting said reference voltage to said meter for indicating the set amount of deviation.
a deviation indicating meter; and means for connecting said reference voltage to said meter for indicating the set amount of deviation.
3. A timing control circuit as defined in claim 2 wherein said connecting means includes an amplifier, a plurality of amplifier gain control circuits corresponding to the number of cylinders of engines, and second switch means for selecting one of said gain control circuits for said amplifier.
4. A timing control circuit as defined in claim 1 including:
an inverter having said increasing ramp voltage as an input and providing said decreasing ramp voltage as an output.
an inverter having said increasing ramp voltage as an input and providing said decreasing ramp voltage as an output.
5. A timing control circuit as defined in claim 3 wherein said connecting means includes an OR circuit having the comparator output and an engine timing signal corresponding to the adjustment reference point as inputs, and third switch means for controlling said OR circuit to select as the output thereof either said comparator output or said engine timing signal.
6. A timing control circuit as defined in claim 5 wherein said means for varying said reference voltage includes a manually actuated potentiometer, with said third switch means actuated by said potentiometer when at the zero deviation position.
7. A timing control circuit as defined in claim 1 wherein said connecting means includes an OR circuit having the comparator output and an engine timing signal corresponding to the adjustment reference point as inputs, and third switch means for controlling said OR circuit to select as the output thereof either said comparator output or said engine timing signal.
8. A timing control circuit as defined in claim 7 wherein said means for varying said reference voltage includes a manually actuated potentiometer, with said third switch means actuated by said potentiometer when at the zero deviation position.
9. A timing control circuit as defined in claim 8 wherein said connecting means includes a one shot multivibrator triggered by said comparator output and providing a trigger pulse for said strobe lamp.
10. A timing control circuit as defined in claim 1 wherein said increasing and decreasing ramp voltages repeat for every engine cylinder firing time, and including an inhibit cir-cuit for preventing lamp triggering except in conjunction with a selected cylinder firing time, said inhibit circuit including an OR circuit having as inputs engine timing signals corresponding to the number 1 cylinder firing time and to the number N cylinder firing time, where N is the number of the cylinder firing just before cylinder number 1, and fourth switch means for selecting the number 1 cylinder timing signal when an advance engine set-ting is desired and selecting the N cylinder timing signal when a retard engine setting is desired.
11. A timing control circuit as defined in claim 10 wherein said connecting means includes a one shot multivibrator triggered by said comparator output and providing a trigger pulse for said strobe lamp, with said inhibit circuit connected to said multivibrator.
12. A timing control circuit as defined in claim 1 wherein said means for producing an increasing ramp voltage comprises:
a voltage controlled oscillator having an output and an input, said oscillator generating a ramp voltage at its output having a slope which is a function of the signal applied at its input;
a comparator circuit having a first reference voltage and said ramp voltage output of said oscillator as inputs and pro-ducing a feedback signal output when said inputs are equal;
an integrator having a pair of inputs and an output con-nected to said input of said oscillator whereby the output of said integrator will determine the slope of said ramp voltage out-put of said oscillator, one of said pair of inputs of said inte-grator being connected to a second reference voltage;
logic circuit means having a pair of inputs and an out-put, one of said inputs being connected to the output of said comparator circuit and the other of said inputs being connected to the ignition of an engine being analyzed, said logic circuit means producing an output equal to said second reference voltage when the signals at said pair of inputs are in coincidence, an output greater than said second reference voltage when the signal at one of said inputs is leading the signal at the other of said inputs and an output less than said second reference voltage when the signal at said one input is lagging the signal at said other input;
means connecting the output of said logic circuit means to the other of said pair of inputs of said integrator; and, resetting means connected to said input of said oscillator.
a voltage controlled oscillator having an output and an input, said oscillator generating a ramp voltage at its output having a slope which is a function of the signal applied at its input;
a comparator circuit having a first reference voltage and said ramp voltage output of said oscillator as inputs and pro-ducing a feedback signal output when said inputs are equal;
an integrator having a pair of inputs and an output con-nected to said input of said oscillator whereby the output of said integrator will determine the slope of said ramp voltage out-put of said oscillator, one of said pair of inputs of said inte-grator being connected to a second reference voltage;
logic circuit means having a pair of inputs and an out-put, one of said inputs being connected to the output of said comparator circuit and the other of said inputs being connected to the ignition of an engine being analyzed, said logic circuit means producing an output equal to said second reference voltage when the signals at said pair of inputs are in coincidence, an output greater than said second reference voltage when the signal at one of said inputs is leading the signal at the other of said inputs and an output less than said second reference voltage when the signal at said one input is lagging the signal at said other input;
means connecting the output of said logic circuit means to the other of said pair of inputs of said integrator; and, resetting means connected to said input of said oscillator.
13. A timing control circuit as defined in claim 12 wherein said logic circuit means includes a first flip-flop hav-ing said reference signal as the input, a second flip-flop hav-ing said feedback signal as the input, and a voltage divider con-nected to voltage sources by said flip-flops, with a point on said voltage divider being said output of said logic circuit means.
14. A timing control circuit as defined in claim 13 including a reset circuit having flip-flop outputs as inputs for resetting both of said flip-flops when both are set.
15. A timing control circuit as defined in claim 14 wherein said reset circuit includes a gate circuit having an en-gine timing pulse as an input for controlling flip-flop resetting.
16. A timing control circuit as defined in claim 12 wherein said resetting means includes a switching circuit for interconnecting the input and output of said voltage controlled oscillator.
17. A timing control circuit as defined in claim 16 including means for connecting said feedback signal to said switching circuit in controlling relation.
18. A timing control circuit as defined in claim 16 including means for connecting an engine timing pulse to said switching circuit in controlling relation.
19. A timing control circuit as defined in claim 14 wherein said means for resetting includes a switching circuit for interconnecting the input and output of said voltage con-trolled oscillator, with said switching circuit and said reset circuit controlled by the same timing signal to reset said flip-flops and said oscillator at substantially the same time.
20. A timing control circuit as defined in claim 19 wherein said timing signal is said feedback signal.
21. A timing control circuit as defined in claim 19 wherein said timing signal is an engine timing pulse.
22. A method of retarding and advancing the trigger-ing of a strobe lamp and sweeping the oscilloscope of an engine ignition analyzer with respect to an adjustment reference point of an engine, including the steps of:
detecting the occurrence of engine ignition timing events;
generating an increasing ramp voltage and a decreasing ramp voltage synchronized with the engine ignition timing;
triggering the oscilloscope sweep with the increasing ramp voltage;
generating a reference voltage of a magnitude varying as a function of the desired strobe lamp triggering deviation from the adjustment reference point;
selecting one of the increasing ramp and ramp voltages depending on whether the strobe lamp triggering is to be retarded or advanced; and triggering the strobe lamp when the selected voltage and the reference voltage are matched.
detecting the occurrence of engine ignition timing events;
generating an increasing ramp voltage and a decreasing ramp voltage synchronized with the engine ignition timing;
triggering the oscilloscope sweep with the increasing ramp voltage;
generating a reference voltage of a magnitude varying as a function of the desired strobe lamp triggering deviation from the adjustment reference point;
selecting one of the increasing ramp and ramp voltages depending on whether the strobe lamp triggering is to be retarded or advanced; and triggering the strobe lamp when the selected voltage and the reference voltage are matched.
23. The method of claim 22 including triggering the strobe lamp in synchronism with the engine number 1 cylinder fir-ing signal when the desired amount of deviation is zero.
24. The method of claim 22 including:
generating a ramp voltage for each cylinder of the engine; and inhibiting strobe lamp triggering except in conjunction with a selected one of the engine cylinder firing signals.
generating a ramp voltage for each cylinder of the engine; and inhibiting strobe lamp triggering except in conjunction with a selected one of the engine cylinder firing signals.
25. The method of claim 24 including inhibiting strobe lamp triggering except for the number 1 cylinder firing signal when retarded triggering is desired and inhibiting strobe lamp triggering except for the number N cylinder firing signal when advanced triggering is desired, where N is the number of the cyl-inder firing just before cylinder number 1.
26. The method of claim 22 wherein said step of gen-erating an increasing ramp voltage synchronized with the engine ignition timing includes the steps of:
detecting the occurrence of an engine ignition event and providing a reference signal corresponding to such event;
generating a ramp voltage;
generating a feedback signal when the ramp voltage reaches a predetermined value; and detecting the difference in phase between the reference signal and the feedback signal and when the signals are out of phase, varying the slope of the ramp voltage in a direction to decrease the phase difference between the signals.
detecting the occurrence of an engine ignition event and providing a reference signal corresponding to such event;
generating a ramp voltage;
generating a feedback signal when the ramp voltage reaches a predetermined value; and detecting the difference in phase between the reference signal and the feedback signal and when the signals are out of phase, varying the slope of the ramp voltage in a direction to decrease the phase difference between the signals.
27. The method as defined in claim 26 including reset-ting the ramp voltage to the initial value after the voltage reaches the predetermined value.
28. The method as defined in claim 26 including reset-ting the ramp voltage to the initial value on occurrence of an engine ignition event.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US05/635,740 US4010414A (en) | 1975-11-26 | 1975-11-26 | Advance and retard timing light |
| US05/635,741 US4010415A (en) | 1975-11-26 | 1975-11-26 | Sweep generator for engine analyzers |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1054222A true CA1054222A (en) | 1979-05-08 |
Family
ID=27092444
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA266,554A Expired CA1054222A (en) | 1975-11-26 | 1976-11-25 | Timing control circuit for an automotive engine ignition analyzer |
Country Status (4)
| Country | Link |
|---|---|
| CA (1) | CA1054222A (en) |
| DE (1) | DE2653626C2 (en) |
| FR (1) | FR2333134A1 (en) |
| GB (1) | GB1559210A (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL7708164A (en) * | 1976-08-16 | 1978-02-20 | Beckman Instruments Inc | DEVICE FOR CALIBRATION OF AN ENGINE BEHAVIOR TESTER. |
| GB8503853D0 (en) * | 1985-02-14 | 1985-03-20 | Bywater J R | Test instrument |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3638107A (en) * | 1966-06-10 | 1972-01-25 | Autoscan Inc | System for displaying the characteristics of ignition signals in an internal combustion engine |
| US3577007A (en) * | 1969-01-21 | 1971-05-04 | Bell & Howell Co | Constant amplitude variable frequency sweep generator |
-
1976
- 1976-11-25 FR FR7635540A patent/FR2333134A1/en active Granted
- 1976-11-25 GB GB4912476A patent/GB1559210A/en not_active Expired
- 1976-11-25 CA CA266,554A patent/CA1054222A/en not_active Expired
- 1976-11-25 DE DE19762653626 patent/DE2653626C2/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| DE2653626C2 (en) | 1982-11-04 |
| DE2653626A1 (en) | 1977-06-02 |
| GB1559210A (en) | 1980-01-16 |
| FR2333134B1 (en) | 1981-05-29 |
| FR2333134A1 (en) | 1977-06-24 |
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