US2787726A - Checking device for electrical ignition circuits in internal combustion engines or the like - Google Patents

Description

Aprll 2, 1957 J BENOlT 2,787,726

CHECKING DEVICE FOR ELECTRICAL IGNITION CIRCUITS IN INTERNAL COMBUSTION ENGINES OR THE LIKE Filed Dec. 15. 1953 2 Sheets-Sheet l mmm mve-rmm T 3511011 April 2, 1957 .g

CHECKING DEVICE R ELECT BUSTION Filed Dec. 15. 1953 BENOIT 2,787,726 ICAL. IGNITION CIRCUITS IN INTERNAL ENGINES OR THE LIKE 2 Sheets-Sheet 2 Ff F799 @m mVEHToR: ITEM BEr/o 'r CHECKING DEVICE FOR ELECTRICAL IGNITION CIRCUITS 1N INTERNAL COIVBUSTION EN- GINES OR THE LIKE Jean Benoit, Paris, France Application December 15, 1953, Serial No. 398,397

Claims priority, application France December 17, 1952 8 Claims. (Cl. 315-22) An object of the present invention is a device allowing the observation and immediate checking of ignition in an internal combustion engine and of the elements of an electric circuit for such an ignition (coil, spark plug etc.) or any similar circuit.

The device according to the invention consists in an electronic assembly comprising:

(a) A cathode ray tube.

(b) Means generating for the horizontal scanning a saw tooth voltage the duration of which (scanning time) is constant whatever may be the repetition frequency of the phenomenon.

(0) Means for starting the scanning in synchronism with the pulse to be studied.

(:1) Means for connecting the pulse to be observed with the vertical deflection members.

(e) Preferably but not necessarily, means for producing luminosity (suitable excitation of the tube cathode) controlled by the horizontal scanning or the pulse to be studied, in order to avoid a damaging of the screen by an excessive intensity received at a given point due to the immobility of the spot in the absence of the pulse to be observed, or between two pulses when the latter are separated by an important time interval.

The means which can be used for the embodiment of the invention are very varied, all kinds of electronic set ups can be adopted. The invention, however, contemplates the following preferred but not limitative set-up.

The horizontal scanning circuit is controlled by two triode tubes (or the equivalent: two pentode tubes, one double triode tube) assembled in a single equilibrium condition circuit with a change over making it possible to direct the pulse to be studied to the grid of one or the other tube according to its polarity or any other equivalent arrangement for this purpose as for instance a rectifier device (such as a double diode) transmitting pulses of constant polarity, whatever the polarity of the pulses received may be and which device can be connected for that reason to one only of the two grids.

This circuit is similar to a multi-vibrator circuit in which the time constant of one of the equilibrium conditions is made infinite by replacing a capacity by a resistance and in which voltages of opposite signs are applied to each grid.

Further, the invention contemplates using the square wave voltage of the circuit thus obtained for creating the luminosity for the screen by a suitable connectionon the cathode of the cathode ray tube.

There is thus obtained, as will be described hereinafter, with reference to the appended electrical diagram, by way of an example of embodiment, a saw tooth horizontal scanning voltage, released by the pulse, with a duration which is independent of the repetition frequency of the phenomenon since, according to the invention:

(a) The pulse itself is used as a synchronism signal for the horizontal scanning and only as a signal.

2,787,726 Patented Apr. 2, 1957 ice (b) The scanning time constant is that defined by its resistance-capacity circuit, i. e. this time is independent of the frequency of the phenomenon (which is very important for the checking of the ignition of an internal combustion engine the speed of rotation of which is highly variable).

The appended drawing comprises:

Figure l, a diagram of an example of embodiment of the invention.

Figures 2 to 10 which are reproductions of curves obtained on the checking device of Figure 1 during the checking of an automobile internal combustion engine.

Referring to Figure 1, it will be seen that the device comprises a cathode ray tube 1 electrically supplied in any suitable manner as regards the heating circuits, etc. and comprising sets of deflecting plates 2 and 3 ensuring, respectively the horizontal and vertical scannings.

The vertical scanning 3 is connected with point B to which are connected through the key 4, the spark plug, the coil, or any other element to be checked. The calibrated potentiometer 5 is interposed for adjusting the curve to a suitable height and for allowing, by means of a suitable calibrating, a measurement of the voltage value of the pulse which is being checked.

The horizontal scanning 2 is connected with point E through the assembly of two triodes 6 and 7 and of the change over 8 making it possible to direct the pulse to the grid of one or the other of the tubes 6, 7, according to its polarity, large resistances being interposed for the double purpose, on the one hand, of not damping too much the circuit from which the pulse is derived, so as not to modify the phenomenon to be checked (for instance not to modify the spark between the electrodes of the spark plug to be checked) and on the other hand to cut down the voltage applied to the grids to suitable values.

The change over 8 can be replaced by any suitable device either to direct the pulse to the suitable grid in accordance to its polarity or to transmit pulses having always the same polarity, whatever the polarity of the pulses received may be.

According to this it is possible to use a double diode, rectifiers, etc.

The grid of tube 6 is normally negative, as results from its connection on the bridge RiRz. The grid of tube 7 is normally positive, as results from its connection on the bridge R3R4. In the absence of any phenomenon, the triode 6 therefore, is locked, the voltage on its plate is the power supply voltage, say +400 v. for instance and the triode 7 passes current, its grid being positively biassed; the plate voltage will depend on the resistances R5 and R7 and will be, for instance 25 volts. The grid voltage of the triode 7 is applied to the tube cathode through a capacity.

The device operates as follows:

If a positive pulse P is connected at E, the change over being arranged for directing it to the triode 6, the grid of this tube becomes suddenly positive, the equilibrium is upset, the tube is conducting and the plate voltage drops suddenly. This voltage drop is transmitted to the. The grid.

grid of the tube 7 through acondenser C1. of the tube 7 thus becomes negative and the tube 7 is locked; the plate voltage on the tube 7 increases suddenly and reinforces the positive voltage of the grid of the tube 6 for the duration of the time constant of the circuit RaCr. This set of operations has the result:

(a) Of generating a saw tooth voltage S in the scanning circuit, the circuit R9C1 of which sets the duration independently of the peculiarities of the pulse proper.

(b) Of causing a voltage drop on the cathode of the tube 7, which gives a square top wave having the effect of causing the emission of electrons in the cathode ray tube andconsequently the luminosity on the screen for the duration of the pulse since it causes a negative pulse on the cathode.

As, on the other hand, the pulse to be studied is sent to the vertical deflecting plates, the phenomenon is recorded on the, oscillograph with a complete synchronism between the two sjcannings, whatever maybe the frequency of repetition of the pulse,- a frequency which may thus be variable.

After this discharge period, the condenser Ci recharges through the resistance R9, the tube- 7 is unlocked and the initial equilibrium'is restored; if the pulse is negative it will be sent to the grid of tube 7lby a suitable switching ofthe change over 8. This grid becoming negative, the tube 7 will be locked and its plate voltage will rise suddenly, supplying to the grid of lamp 6 a sudden posi-' tive voltage which makes this tube conducting and the rocess is re eated as in the previous case.

It will be obvious that other electronic circuit may ive the same result; in particular, the two triode tubes 6 and 7 may be replaced by a double triode or by two pentodes; other types of discharge tubesrnay be used (thyratron) the invention still consisting in starting their discharge by the pulse itself. The appended drawing represents a particular and preferred embodiment of the invention, not limitative however.

The connecting of the apparatus on the element to be checked is effected at point B by any suitable means such as a plug or mouth 4 with an interposition of any suitable resistance, a ground connection of the body consisting, in the case of an internal combustion engine, in connecting the body of the motor to'the body of the checking oscillograph, being also provided. 7

Figures 2 to l( are typical pictures of the curves obtained when checking the ignition of an internal combustion engine with a device according to the invention.

Figure 2 is the curve obtained with a normal ignition circuit; taken at the terminals of thelspark plug giving sparks. V

Figure 3 is the curve obtained with a normal ignition circuit taken on the spark plug Wire, the spark plug being disconnected (no spark).

Figure 4 shows a fouled spark plug, the ignition taking place however, the curve being also derived from the terminals of the spark plug.

The curve of Figure 6 means: a condenser fault, with no spark obtained, either no spark actually occurring or' ductive; means for positively biasing the control electrode of said second device so that said second device is normally conductive; means for coupling the anodes of each of said devices to the control electrodes of each of the other devices, respectively; a cathode ray tube having a pair of horizontal deflecting plates and a pair of vertical deflecting plates; means for applying the pulse to be tested to the control electrode of one of said devices whereby. this device reverses its'conductive state and emits an impulse through said coupling means to reverse the conductive state of the other device; means for connecting the anode of the normally conducting'dcvice to said pair of horizontal defiecting'plates; and means included in said trigger circuit for synchronizing the emission of electrons in said cathode ray tube with the application of said pulse to be tested.

2. A pulse testing apparatus comprising, in combination, a trigger circuit having a first and a second triode; power supply means for supplying operating potentials for said triode's; means for negatively biasing the control elec-.

trade of said first triode so thatlsaid first triode is normally non-conductive; means for positively biasing the control electrode of said second triode sothat said second triode, is normally conductive; means for coupling ,the V anodes of each of said triodes to the control electrodes of each of the other triodes, respectively; a cathode ray tube having a pair of horizontal deflecting plates and a pair of vertical deflecting plates; means for applying the pulse to be tested to the control electrode of one of said triodes whereby this triode reverses its conductive state and emits an impulse through said coupling means to reverse the conductive state of the other triode; means for connecting the anode of the normally conducting triode to said pair of horizontal deflecting plates; means for applying the trode of the first half of said twin triode so that'said first the curve being taken on the spark plug wire the latter The curve in Figure 10 means that the coil is defective (curve taken at the coil).

These curves show conclusively the interest of the device which makes it possible to detect immediately the existence of a fault, its nature and origin.

The apparatus, obviously, is not limited to its application to the checking of internal combustion engines, any suitable apparatus comprising an electric circuit in which regular shaped pulses are repeated may be checked in an identical manner.

I claim:

1. A pulse testingapparatus comprising, in combination, a trigger circuit having a first and a second electron discharge device, each of. said devices having at least a cathode, an anode and a control electrode; power supply half is normally non-conducting;'means for positively biasing the control electrode of the second half of said twin triode so that said second half is normally conductive; means for coupling the anodes of each half of said twin triode to the control electrode of the other half respec V tivelyja cathode ray tube having a pair of horizontal deflecting plates and a pair of verticaldeflecting plates;

means for applying the pulse to be tested to-the control ing the pulse to be tested to said pair of vertical deflecting plates; and means included in said .trigger circuit for synchronizing the emission of electrons in said cathode ray tube with the application of said pulse to be tested.

4. A pulse testing apparatus comprising, in combina-' tion, a trigger circuit having a first and a second electron discharge device, each of said devices having at least a cathode, an anode and a control electrode; power supply means for supplying operating potentials for .said device, said operating potentials including a ground potential for said cathodes; mcanslfor negatively biasing the control electrode of said firstdevice so that said first device isnorm'ally non-conductive; a capacitor connected be tween the anode of said. first device and the control electrode of saidsecond device; a first resistor connected between said control electrode and ground potential; a sec- 0nd resistor connected between the anode of said second device and the control electrode of said first device; av

cathode ray tube having a pair of horizontal deflecting plates and a pair of vertical deflecting plates; means for applying the pulse to be tested to the control electrode of one of said devices whereby this device reverses its conductive state and emits an impulse through said coupling means to reverse the conductive state of the other device; means for connecting the anode of the normally conducting device to said pair of horizontal deflecting plates; means for applying the pulse to be tested to said pair of vertical deflecting plates; and means included in said trigger circuit for synchronizing the emission of electrons in said cathode ray tube with the application of said pulse to be tested.

5. A pulse testing apparatus comprising, in combination, a trigger circuit having a first and a second electron discharge device, each of said devices having at least a cathode, an anode and a control electrode; power supply means for supplying operating potentials for said devices; means for negatively biasing the control electrode of said first device so that said first device is normally nonconductive; means for positively biasing the control electrode of said second device so that said second device is normally conductive; means for coupling the anodes of each of said devices to the control electrodes of each of the other devices, respectively; a cathode ray tube having a pair of horizontal deflecting plates, a pair of vertical deflecting plates, and a cathode; means for applying the pulse to be tested to the control electrode of one of said devices whereby this device reverses its conductive state and emits an impulse through said coupling means to reverse the conductive state of the other device; means for connecting the anode of the normally conducting device to said pair of horizontal deflecting plates; means for applying the pulse to be tested to said pair of vertical deflecting plates; and means for connecting the cathode of said second device to the cathode of said cathode ray tube for synchronizing the emission of electrons in said cathode ray tube with the application of said pulse to be tested.

6. A pulse testing apparatus comprising, in combination, a trigger circuit having a first and a second electron discharge device, each of said devices having at least a cathode, an anode and a control electrode; power supply means for supplying operating potentials for said devices; means for negatively biasing the control electrode of said first device so that said first device is normally nonconductive; means for positively biasing the control electrode of said second device so that said second device is normally conductive; means for coupling the anodes of each of said devices to the control electrodes of each of the other devices, respectively; a cathode ray tube having a pair of deflecting plates and a pair of vertical deflecting plates; means for applying a positive pulse to be tested to the control electrode of said first device whereby this device starts to conduct and emits a negative impulse through said coupling means to block conduction of said second device; means for connecting the anode of the normally conducting device to said pair of horizontal deflecting plates; means for applying the pulse to be tested to said pair of vertical deflecting plates; and means included in said trigger circuit for synchronizing the emission of electrons in said cathode ray tube with the application of said pulse to be tested.

7. A pulse testing apparatus comprising, in combination, a trigger circuit having a first and a second electron discharge device, each of said devices having a least a cathode, an anode and a control electrode; power supply means for supplying operating potentials for said devices; means for negatively biasing the control electrode of said first device so that said first device is normally non-conductive; means for positively biasing the control electrode of said second device so that said second device is normally conductive; means for coupling the anodes of each of said devices to the control electrodes of each of the other devices, respectively; a cathode ray tube having a pair of horizontal deflecting plates and a pair of vertical deflecting plates; means for applying a negative pulse to be tested to the control electrode of said second device whereby this device becomes non-conductive and emits a positive impulse through said coupling means to initiate conduction in said first device; means for connecting the anode of the normally conducting device to said pair of horizontal deflecting plates; and means included in said trigger circuit for synchronizing the emission of electrons in said cathode ray tube with the application of said pulse to be tested.

8. A pulse testing apparatus comprising, in combination, a trigger circuit having a first and second electron discharge device, each of said devices having at least a cathode, an anode and a control electrode; a power supply means for supplying operating potentials for said devices, said operating potentials including a ground potential for said cathodes; means for negatively biasing the control electrode of said first device so that said first device is normally non-conductive; means for positively biasing the control electrode of said second device so that said second device is normally conductive; a capacitor connected between the anode of said first device and the control electrode of said second device; a first resistor connected between said control electrode and ground potential; a second resistor connected between the anode of said second device and the control electrode of said first device; a cathode ray tube having a pair of horizontal deflecting plates, a pair of vertical deflecting plates, and a cathode; means for applying the pulse to be tested to the control electrode of one of said devices whereby this device reverses its conductive state and emits an impulse through said coupling means to reverse the conductive state of the other device; means for connecting the anode of the normally conductive device to said pair of horizontal deflecting plates; means for applying the pulse to be tested to said pair of vertical deflecting plates; and means for connecting the cathode of said second device to the cathode of said cathode ray tube for synchronizing the emission of electrons in said cathode ray tube with the application of said pulse to be tested.

References Cited in the file of this patent UNITED STATES PATENTS 2,373,145 Sensiper et al Apr. 10, 1945 2,402,168 Lifschutz June 18, 1946 2,414,323 Moe Jan. 14, 1947 2,420,516 Bischolf May 13, 1947 2,455,283 Valley Nov. 30, 1948 2,477,615 Isbister Aug. 2, 1949

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