AVERAGE TIMING METHOD AND APPARATUS FOR INTERNAL COMBUSTION ENGINES

• US 3,753,082 A
• Filed: 01/20/1972
• Issued: 08/14/1973
• Est. Priority Date: 01/20/1972
• Status: Expired due to Term

• Current Assignee: Arthur R. Crawford, Glenroy W. Barnett, Joseph R. Pottebaum, Richard E. Porter
• Original Assignee: Arthur R. Crawford, Glenroy W. Barnett, Joseph R. Pottebaum, Richard E. Porter
• Inventors: Pottebaum, Joseph R., Crawford, Arthur R., Barnett, Glenroy W., Porter, Richard E.
• Primary Examiner(s): Lynch, Michael J.
• Application Number:
  US05/219,416
• Time in Patent Office: 572 Days
• Field of Search: 324/15-18 73/116,117.3,118R,119A
• US Class Current: 324/392
• CPC Class Codes: F02P 17/02 Checking or adjusting ignition timing

Abstract

There is disclosed a method and apparatus for internal combustion engine timing based on measurement of the advance or retard of the firing of each spark plug with respect to a reference derived from the top dead center position of the piston for the number one cylinder. The engine timing is adjusted so that the average value of the advance or retard for all plugs equals a predetermined design value. A variable frequency oscillator is phase-locked by signals representing individual spark plug firing to operate at a frequency of 3,600 pulses per engine revolution. A reference related to the top dead center position of piston for the first cylinder is determined by sensing a notch in the engine damper or fan pulley, and is used to produce a series of pseudo damper pulses offset from the top dead center positions of the various pistons by 45 degrees by dividing the output of the variable frequency oscillator and selecting pulses to define the pseudo damper pulse interval based on the number of cylinders in the engine being timed. Timing measurement is achieved by counting the number of pulses between firing of a plug and the associated pseudo damper pulse over several complete engine operating cycles, averaging the result and removing the 45* offset. Digital display, printout, upper and lower limit computation and actual engine RPM measurements are also provided.

Claims

1. An internal combustion engine timer comprising:

reference position sensing means to coperate with an engine under adjustment to generate a reference pulse at a predetermined angular position of the engine crankshaft for each engine revolution;

ignition sensing means to cooperate with the engine under adjustment to generate a pulse coincident with the firing of each spark plug;

means responsive to the succession of spark pulses to generate a master pulse train having a constant number of pulses per engine revolution, each pulse thereby representing a predetermined fraction of an entire 360 degree revolution;

means responsive to each reference position pulse for selecting groups of said master pulses to define a set of pseudo reference pulses, each of said pseudo reference pulses representing a predetermined angular position of the engine crankshaft with reference to top dead center position for the respective pistons, said set of peudo reference pulses including a pulse for each cylinder of the engine;

means for establishing a timing interval between each of the spark pulses and the pseudo reference pulse for the associated cylinder, said timing interval establishing means comprising means for producing a train of timing pulses and means for counting the number of said timing pulses between each spark pulse and its associated pseudo reference pulse; and

means for counting the average number of master pulses generated during a succession of timing intervals as a measure of the average firing angle for all of the cylinders.

2. Engine timing apparatus as defined in claim 1 wherein said ignition sensing means comprises a pickup adapted to be electrically coupled to the output of the spark coil of the engine under adjustment, said pickup being responsive to the energy fields caused by the opening and closing of the distributor points;

signal processing means coupled to said pickup and responsive to that portion of the pickup output corresponding to the opening of said distributor points to generate said spark signal.

3. Engine timing apparatus as defined in claim 2 wherein said signal processing means comprises amplifier means;

circuit means for differentiating said pickup output to produce a derivative waveform including a portion corresponding to the opening of said points, the latter being characterized by a level substantially exceeding that of other portions of said derivative waveform;

means for establishing an operating threshold for said amplifying means above the magnitude of all portions of said derivative waveform except the portion corresponding to the opening of said points; and

means for coupling said derivative waveform to the input of said amplifying means whereby said amplifier operates only during an interval corresponding to the opening of the points.

4. An internal combustion engine timer comprising:

reference position sensing means to cooperate with an engine under adjustment to generate a reference pulse at a predetermined angular position of the engine crankshaft for each engine revolution;

ignition sensing means to cooperate with the engine under adjustment to generate a pulse coincident with the firing of each spark plug;

means responsive to the succession of spark pulses to generate a master pulse train having a constant number of pulses per engine revolution, each pulse thereby representing a predetermined fraction of the entire 360* revolution;

means responsive to each reference position pulse for selecting groups of said master pulses to define a set of pseudo reference pulses, each of said pseudo reference pulses representing a predetermined angular position of the engine crankshaft with reference to the top dead center position for the respective pistons said set of pseudo reference pulses including a pulse for each cylinder of the engine;

means for establishing a timing interval between each of the spark pulses and the pseudo reference pulse for the associated cylinder, said timing interval establishing means comprising means for producing a train of timing pulses and means for counting the number of said timing pulses between each spark pulse and its associated pseudo reference pulse; and

means for counting the number of master pulses during said timing interval as a measure of the firing angle for the cylinders corresponding to the respective counting intervals.

5. Engine timing apparatus as defined in claim 4 wherein said reference position sensing means comprises a pickup adapted to be positioned in non-contacting proximity to a member rotating with the crankshaft of the engine under adjustment, said pickup being responsive to the passage within its field of sensitivity of a predetermined portion of said member to generate an output pulse;

and signal processing means responsive to said pickup output pulse for generating said reference pulse approximately coincident with the center of the pickup output pulse.

6. Engine timing apparatus as defined in claim 5 wherein said pickup output pulse is characterized by positive and negative portions of approximately equal duration separated by a zero signal level crossing;

and wherein said signal processing means includes means responsive to said zero crossing to generate said reference pulse.

7. Engine timing apparatus as defined in claim 6 wherein said signal processing means comprises a first transistor circuit;

means responsive to the level of the pickup output pulse to generate a control signal for said first transistor circuit;

means to differentiate the pickup output signal and to apply the resulting derivative signal to said transistor circuit;

biasing means responsive to said control signal to establish a conduction threshold for said transistor at a predetermined level below the peak value of the derivative signal;

a normally conductive second transistor circuit;

means coupled to the output of said second transistor circuit for providing said reference pulse;

means coupling the signal output of said first transistor circuit to the signal input of the second transistor circuit; and

means for biasing said second transistor circuit to be non-conductive when said first transistor circuit is conductive, and to be conductive when said first transistor circuit is nonconductive.

8. Engine timing apparatus as defined in claim 4 wherein said master pulse train generating means comprises a digital phase locked loop responsive to said spark pulses to generate said train of master pulses at a frequency equal to a selected multiple of the spark repetition frequency.

9. Engine timing apparatus as defined in claim 8 wherein digital phase locked loop is operative to generate 3,600 pulses per engine revolution.

10. Engine timing apparatus as defined in claim 8 further including means to vary the ratio of the repetition frequency of the master pulse train to the spark repetition frequency in accordance with the number of cylinders in the engine under adjustment such that said pulse train contains a substantially constant number of pulses per engine revolution, independent of the number of cylinders.

11. Engine timing apparatus as defined in claim 8 wherein said phase locked movement comprises a voltage controlled oscillator for generating said pulse train;

divider means coupled to the output of said voltage controlled oscillator;

phase detector means having one input coupled to the output of said divider, and the other input coupled to said spark pulses and means coupling the output of said phase detector to said voltage controlled oscillator to adjust the frequency thereof in accordance with the phase difference between the succession of spark pulses and the output of said divider.

12. Engine timing apparatus as defined in claim 11 further including means responsive to said spark pulse to generate a DC analog of the repetition rate thereof;

and means for coupling said DC analog to said voltage controlled oscillator further to control the frequency of its output.

13. Engine timing apparatus as defined in claim 12 wherein said DC analog signal generator comprises means responsive to each spark pulse to generate a further pulse of predetermined duration depending on the number of cylinders in the engine under adjustment;

and means to integrate the resulting train of further pulses.

14. Engine timing apparatus as defined in claim 13, further including means to adjust the duration of said further pulses in accordance with the ratio 1:

2/3;

1/2 for four, six, and eight-cylinder engines, respectively.

15. Engine timing apparatus as defined in claim 13 wherein said further pulse generating means comprises a single shot multi-vibrator, means for selectively adjusting the operating period of said single shot multi-vibrator in accordance with the number of cylinders in the engine under adjustment such that the width of said further pulses are in the ratio 1:

2/3;

1/2 for engines having four, six, and eight cylinders, respectively.

16. Engine timing apparatus as defined in claim 14 wherein said divider comprises counter means, means for selecting the counting base of said counter means in accordance with the number of cylinders in the engine under adjustment in accordance with the ratio 1:

2/3;

1/2 for engines having four, six, and eight cylinders, respectively.

17. Engine timing apparatus as defined in claim 11 wherein said divider comprises variable base counting means;

and means for adjusting the base of said counting means in accordance with the ratio 1;

2/3;

1/2 for engines having four, six, and eight cylinders, respectively.

18. Engine timing apparatus as defined in claim 11 wherein said phase detector comprises first pulse stretching means coupled to the output of said divider and operative to covert the succession of divider output pulses into a squarewave;

second pulse stretching means coupled to said spark signal generator and operative to convert the succession of spark pulses into a sqUarewave;

a phase detector circuit coupled to the outputs of said first and second pulse stretching circuits and operative to generate a DC analog of the phase error between said squarewaves.

19. Engine timing apparatus as defined in claim 18 wherein each of said first and second pulse stretching means comprises a variable period single shot multi-vibrator;

means respectively coupling said divider output and said spark pulse signals as the triggering inputs for said single shot multi-vibrators;

a sensing means coupled to the output of each of said multi-vibrators, and responsive to the on and off time of the outputs thereof to provide respective DC signals representative of the difference between said on and off times; and

feedback means for each multivibrator responsive to said difference signals for adjusting the period of the respective multi-vibrator to minimize the values of said difference signals.

20. Engine timing apparatus as defined in claim 19 wherein each of said sensing means comprises a first circuit responsive to the level of the single shot output when triggered;

second circuit means responsive to the level of said single shot output when in its rest condition, said first circuit means including means to block a signal level corresponding to the triggered condition of said single shot, and a second circuit means including means to block the signal level corresponding to the untriggered condition of said single shot, each of said sensing means further including integrator means coupled to the output of the respective first and second circuits to generate DC analog signals corresponding to the durations of the on and off times for the associated single shots; and

means coupled to the output of said integrator circuits to provide a signal representative of the difference between said DC pulse width analogs; and

wherein said feedback means comprises a time constant circuit coupled to the associated single shot, a signal controlled impedance element connected in the current path of said time constant circuit, and means coupling said difference signal to said signal controlled impedance element to adjust the impedance thereof, thereby effectively varying the time constant of the time constant circuit.

21. Engine timing apparatus as defined in claim 8 wherein said phase locked loop includes a voltage controlled oscillator to produce said master pulse train;

means for comparing the output of said voltage controlled oscillator with the train of spark pulses to generate a first control signal for said voltage controlled oscillator;

means to generate a DC analog of the speed of the engine under adjustment; and

means for coupling said DC speed analog as a further control signal for said voltage controlled oscillator.

22. Engine timing apparatus as defined in claim 21 wherein said means for generating said DC engine speed analog comprises means responsive to each spark pulse to generate a further pulse of predetermined duration as a function of the number of cylinders of the engine under adjustment;

and means to integrate the resulting train of further pulses to generate said DC analog.

23. Engine timing apparatus as defined in claim 22 wherein said further pulse generating means comprises a single shot, means for selectively adjusting the operating period of said single shot such that the pulse width varies in accordance with the ratio 1:

2/3;

1/2 for engines having four, six, and eight cylinders, respectively.

24. Engine timing apparatus as defined in claim 4 wherein said pseudo reference pulse generating means comprises a counter;

means coupling the master pulse train as the input to said counter;

pulse collecting means to provide a succession of pulses as said pseudo reference pulses corresponding to selected output count states of said counter; and

means to reset said counter in response to each engine reference pulse.

25. Engine timing apparatus as defined in claim 24 wherein said pulse collecting means includes a firsT logic circuit to select two counts per engine revolution corresponding to two of the four pseudo reference pulses for a four-cycle engine;

second logic means to select three counts per engine revolution corresponding to three of the six pseudo reference pulses for a six-cylinder engine;

a third logic circuit to select four counts per engine revolution corresponding to four of the eight pseudo reference pulses for an eight-cylinder engine; and

means for selectively actuating said first, second, or third logic circuits.

26. Engine timing apparatus as defined in claim 25 wherein said master pulse train is a frequency of 3,600 pulses per engine revolution;

and further including means coupled to said counter to generate a strobe pulse having a duration equal to one pulse of said master pulse train each time the state of said counter increases by 100 counts; and

means to condition said first, second, and third logic circuits in response to said succession of strobe pulses.

27. Engine timing apparatus as defined in claim 24 adapted to measure the timing angles of engines designed to fire before or after the top dead center position for each piston and including means to select retard mode operation for said apparatus corresponding to an engine designed to fire after top dead center, and to select advance mode operation for said apparatus corresponding to an engine designed to fire before top dead center;

means responsive to selection of the advance mode of operation to delay each pseudo reference pulse for an interval corresponding to a predetermined number of pulses of said master pulse train; and

responsive to selection of the retard mode of operation to pass said pseudo reference pulses with essentially no delay. 28.Engine timing apparatus as defined in claim 27 wherein said delay means comprises a further counter;

means for coupling said master pulse train to the input of said counter;

logic circuit means coupled to the output of said counter to generate a pulse at a predetermined count corresponding to the desired delay interval;

means to reset said counter in response to said delay pulse; and

means to restart said counter in response to the next pseudo reference pulse following a reset.

29. Engine timing apparatus as defined in claim 24 wherein said apparatus is adapted to measure the timing of engines designed to fire both before and after the top dead center position of its pistons and including means to select retard mode operation for adjusting an engine designed to fire after top dead center, and to select advance mode operation for adjusting an engine designed to fire before top dead center;

means responsive to selection of the retard mode of operation to generate each of said pseudo reference pulses at a position in the engine revolution cycle corresponding to 45 degrees before top dead center for each piston; and

means responsive to selection of the advance mode of operation to delay each pseudo pulse such that the same appears at a point in the engine revolution 45* after top dead center for the associated cylinder.

30. Engine timing apparatus as defined in claim 29 wherein said delay means comprises a further counter means for coupling said master pulse train to the input of said counter, logic circuit means coupled to the output of said counter to generate a delayed pulse at a predetermined count corresponding to the desired delay interval;

means to reset said counter in response to said delayed pulse; and

means to restart said counter in response to the next pseudo reference pulse following a reset.

31. Engine timing apparatus as defined in claim 24 wherein said apparatus is adapted to measure the timing of engines designed to fire both before and after the top dead center position of its pistons and including means to select retard mode operation for adjusting an engine designed to fire after top dead center, and to select advance mode operation for adjusting an engine designed to fire before top dead center;

meanS responsive to selection of the retard mode of operation to generate each of said pseudo reference pulses at a position in the engine revolution cycle corresponding to 45* before top dead center for each cylinder;

means responsive to selection of the advance mode of operation to delay each pseudo pulse such that the same appears at a point in the engine revolution 45* after top dead center for the associated cylinder;

means for selecting the number of cylinders in the engine being adjusted, and means responsive to selection of an eight-cylinder engine to inhibit the operation of said delay circuit, thereby preventing said delay for advance mode operation.

32. Engine timing apparatus as defined in claim 24 adapted to measure the timing angles of engines designed to fire before or after the top dead center position for each piston and including means to select retard mode operation for said apparatus corresponding to an engine designed to fire after top dead center, and to select advance mode operation for said apparatus corresponding to an engine designed to fire before top dead center;

means responsive to selection of the advance mode of operation to delay each pseudo reference pulse for an interval corresponding to a predetermined number of pulses of said master pulse train; and

responsive to selection of the retard mode of operation to pass said pseudo reference pulses with substantially no delay;

means for selecting the number of cylinders in the engine under adjustment; and

means responsive to selection of an eight-cylinder engine for inhibiting operation of said delay circuit whereby said pseudo reference pulses are not delayed for advance mode operation.

33. A method of timing an internal combustion engine comprising the steps of:

sensing a predetermined reference position of the engine crankshaft in relation to the top dead center position for a particular cylinder;

sensing the occurrence of each ignition;

generating a master pulse train having a constant number of pulses per engine revolution;

selecting predetermined ones of said master pulses following the sensing of the reference position during a revolution to form a set of pseudo reference pulses each having a particular angular relationship to the top dead center position for one of the cylinders of the engine being timed;

establishing a timing interval between each spark pulse and the associated pseudo reference pulse; and

averaging the number of master pulses during a predetermined number of timing intervals as a a measure of the average timing angle for all the cylinders.

34. A method of timing an internal combustion engine as defined in claim 33 further including the steps of displaying a visual representation of said average value of said timing angle;

and adjusting the distributor rotor of the engine until the average value of the timing angle is acceptably close to the specified design value.

35. A method of timing an internal combustion engine as defined in claim 33 further including the steps of selecting the particular angular relationship between the pseudo reference pulses and the top dead center position for the associated cylinder such that, for retard operation, in which the engine is adjusted to fire after top dead center, the spark pulse always follows the associated pseudo reference pulse, and for advance operation, in which the engine is adjusted to fire prior to top dead center, the spark always occurs prior to the associated pseudo reference pulse.

36. The method of timing an internal combustion engine as defined in claim 35 wherein each of said pseudo reference pulses are selected to occur 45* after top dead center for advance operation, and 45* before top dead center for retard operation.

37. The method of timing an internal combustion engine as defined in claim 36 further including the steps of displaying a visual representation of said average timing angle;

and adjusting the distributor rotor of the engine until the average vAlue of the timing angle is acceptably close to the specified design value.

38. A method of timing an internal combustion engine as defined in claim 33 wherein said step of generating said master pulse train comprises the steps of phase locking an oscillator to a train of spark pulses coincident with the ignitions of the engine under adjustment.

39. A method of timing an internal combustion engine as defined in claim 38 wherein said steps of phase locking said oscillator comprises comparing the output of said oscillator with said succession of spark pulses;

and controlling the operating frequency of said oscillator in accordance with the phase difference between said oscillator output and said spark pulses.

40. A method of timing an internal combustion engine as defined in claim 39 further including the steps of generating a DC analog representative of the speed of the engine being timed, and further controlling the frequency of said oscillator based on said DC analog signal.

41. A method of timing an internal combustion engine as defined in claim 40 wherein the steps of generating said DC analog comprises the steps of integrating the succession of spark pulses;

and compensating for the different number of pulses per revolution in engines having different numbers of cylinders such that, at a given RPM, the result of the integration is independent of the number of cylinders.

42. The method of timing an internal combustion engine as defined in claim 41 wherein the step of compensating for said different number of cylinders comprises generating a variable width pulse in response to each spark pulse;

and adjusting the width of said variable width pulse according to the ratio 1;

2/3;

1/2 for timing engines having four, six, and eight cylinders, respectively.