US3722488A

US3722488A - Capacitor discharge system

Info

Publication number: US3722488A
Application number: US00126431A
Authority: US
Inventors: T Swift; E Brayley
Original assignee: T Swift; E Brayley
Current assignee: Prestolite Electric Inc
Priority date: 1971-03-22
Filing date: 1971-03-22
Publication date: 1973-03-27
Anticipated expiration: 1990-03-27
Also published as: CA951373A; DE2203205A1; GB1373936A

Abstract

A breakerless ignition system of the capacitor discharge type for an engine is disclosed with the energy being supplied by a simplified magneto having a magnetic structure energized by a rotor with a single permanent magnet group to create a charging current for the capacitor and a trigger current to change the conductance state of a silicon-controlled-rectifier to discharge the current stored in the capacitor into an ignition coil to provide the ignition spark in the secondary thereof. The magnetic arrangements between the parts provide an automatic timing advance with increase in speed of the engine. Improved means are provided for temperature compensation by a bifilar winding on the trigger coil of positive temperature coefficient wire of nickel or the like. Anti-reverse rotation protection is also provided.

Description

United States Patent 1 Swift et a1.

[54] CAPACITOR DISCHARGE SYSTEM 1 1 Mar. 27, 1973 3,464,397 9/1969 Burson ..123/148 E 7 E. 'n l l 51 Inventors Thoinas Swlft gfied Przmary ExaminerLaurence M. Goodndge Elwin J. Brayley, East Longmeadow, both of Mass Asszstant Exammer-Cort Flmt Attorney-D. Henry Stoltenberg [73] Assignee: Eltra Corporation, Toledo, Ohio [57] ABSTRACT [22] Fled: 1971 A breakerless ignition system of the capacitor [21] Appl. No.: 126,431 discharge type for an engine is disclosed with the energy being supplied by a simplified magneto having a magnetic structure energized by a rotor with a single [52] U.S. Cl ..123/149 D, 123/148 E, 123/149 R permanent magnet group to create a charging current [51] Int. Cl ..F02p 3/06 for the capacimr and a trigger curl-em to change the [58] Flew Search "123/148, 149; 310/153 conductance state of a silicon-controlled-rectifier to 315/209 T discharge the current stored in the capacitor into an ignition coil to provide the ignition spark in the secon- [56] References Cited dary thereof. The magnetic arrangements between the parts provide an automatic timing advance with in- UNITED STATES PATENTS crease in speed of the engine. Improved means are 3,524,438 8/1970 Janisch ..123/149c Provided for temperature Compensation y a bifilaf 3,515,109 5/1968 F I 123 49 winding on the trigger coil of positive temperature 3,554,179 1/1971 Burson .....123/149 A coefficient wire of nickel or the like. Anti-reverse 3,598,098 8/1971 Sohner ..123/148 E rotation protection is also provided. 3,576,183 4/1971 Miyamoto ..123/148 E 3,599,615 8/1971 Foreman 123/149 c 3 Chums, 8 Drawing Flgllres 3,398,353 8/1968 Noddin et al. ..123/148 E A B c 0 E l l I i I TRIGGER 11211.21 COIL 34 I I ,1\' |/-+H16H SPEED 1 1 L Z 1 SCR TRIGGER LEVEL II N! l TRIGGER Low SPEED VOLTS 1N 1 con. 34 1 I l l l I l I l I 1 I11 I CHARGING 1 I wmnme vours IN 1 con. 32 I I 11 l l CAPACITOR 1 VOLTS IN l GENERATING CORE FLUX CONDENSER c0 1 PATENTEUHARZYIQYS 722,4

SHEET 1 BF 2 34b 32b I6 g INVENTORS.

THOMAS E. S T ELWIN J. BR EY BY ATTORNEY M N P I I I I I I III I I I I I I I I I I I I I I I I 360 -I+-I I I I I I I I l I I I PATENIEUIIARZ SHEET 20F 2 A a c D E I I I I I I I I TRIGGER I ANGULAR CHARGING FLUX IN I POSITION WINDING COI 34 CURRENT I I I -IIIGII SPEED Y I I I J I u SCR TRIGGER LEVEL 11 I LOW SPEED TRIGGER TRIGGER VOLTS IN I RI VOLTS COIL 34 I I I \J I I Y I I I I I I I m I I CHARGING I CHARGING WINDING WINDING VOLTS IN I VOLTS COIL'32 I I I m I I I I cAPAcIToR I I I VOLTS IN I I I coNDENsER I w l I I l I I I I I I I I GENERATING CORE FLUX IN ELEMENT 32a INVENTORS. THOMAS E. SWIFT Y ELWIN J. BRAYLEY ATTORNEY Z CAPACITOR DISCHARGE SYSTEM The present invention contemplates the provision of a capacitor discharge ignition system for engines which is supplied with energy and controlled by a simple magneto which is capable of being economically produced and also has its elements arranged for easy service in the field. The magnetic portions of the magneto are arranged to give an automatic time advance when a predetermined speed of the engine is attained, with further provision being made for temperature compensation and means to prevent the engine running in reverse above clutch engagement speed in a conventional drive.

It is therefore a principal object of this invention to provide a capacitor discharge ignition system for an engine, the energy for which and control thereof are provided by an electric generator driven by the engine, having a magnetic stator arrangement cooperating with a single rotating permanent magnet group to provide a single positive trigger pulse having two peaks of varying height to provide an automatic spark advance when the engine is operating at a predetermined speed of rotation.

It is a further object of this invention to provide a simplified construction of an electric generator capable of being economically produced and which is adapted to ready adjustment and repair while in service in the field.

It is a further object of this invention to provide an electric generator for supplying power and control to a capacitor discharge ignition system for an engine where temperature compensation is provided by the inherent characteristic of a trigger coil to maintain the timing characteristic substantially constant and where special means are provided in the ignition circuit to prevent reverse rotation of the engine by preventing spark discharge for the engine when such rotation occurs above the conventional clutch engagement speed.

Other objects and advantages of this invention relating to the arrangement, operation and function of the related elements of the structure, to various details of construction, to combinations of parts and to economies of manufacture will be apparent to those skilled in the art upon consideration of the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

FIG. 1 is a schematic plan view of the stator and rotor of the magneto showing an initial relation of the magnetic parts.

FIG. 2 is a schematic plan view of the parts shown in FIG. 1 after rotation of the rotor of about 300 in counterclockwise direction.

FIG. 3 is a plan view similar to FIGS. 1 and 2 with the rotor rotated further in a counterclockwise direction.

FIG. 4 is a plan view similar to the other figures with the rotor rotated further in a counterclockwise direction.

FIG. 5 is a curve group of the characteristics of the relation between flux and voltage at relative times in counterclockwise rotation.

FIG. 6 is a schematic diagram of connections of the ignition circuit.

FIG. 7 is a schematic diagram of connection of a simplified ignition circuit, and

FIG. 8 is a curve group similar to FIG. 5 of the circuit shown in FIG. 7 in clockwise rotation.

Referring to the drawings, particularly to FIGS. 1-4, a rotor element 10 is shown on which is affixed a magnetic assembly 12 consisting of a permanent magnet 14 and a pair of laminated pole shoes 16 and 18 which cooperate through the air gap 20. The rotor element 10 is preferably the flywheel of an internal combustion en gine which has an ignition system which is adapted to be energized and controlled by the elements about to be described. The ignition system includes a high voltage induction coil C, the secondary S of which fires a spark plug SP in the engine cylinder in timed relation with the rotation of the engine flywheel, and the primary P of which is energized by a capacitor CD which is discharged through the primary SP by a semiconductor switch SCR such as a silicon-controlled-rectifier to create the voltage in the secondary which fires the spark plug P in its timed relation, all as shown in FIG. 6, which is a schematic diagram of connections of the ignition circuit which will be described further hereinafter.

The rotor 10, with its permanent magnet group 12 cooperates with a stationary stator element 30 to which are affixed a pair of

coils

32 and 34, of which coil 32 is a charging coil for the capacitor CD and coil 34 is a trigger coil to control the gate G of the switch SCR. The charging coil 32 is provided with a U-shaped laminated magnetic element 32a, affixed to that stator element 30 in any convenient conventional manner so that the terminal faces 32b and 32c of the legs of the magnetic element 32 cooperate with the periphery of the flywheel 10 by a small air gap in a manner that the

pole shoes

16 and 18 which are curved to terminate in the periphery of the flywheel, create varying magnetic responses in the magnetic circuits formed. It will be noted that the flywheel rotates in a counterclockwise direction as shown in FIG. 1, so that pole shoe l6 first rotates past face 320 and then past 32b, with pole shoe 18 in the lagging position, separated from pole shoe 16 by air gap 20.

The trigger coil 34 is also provided with a laminated magnetic core 34a which is affixed to the stator 30 in any convenient manner so that the lower terminal face 34b also cooperates with the periphery of the flywheel 10 by a small air gap so that it comes into the magnetic influence of the

pole shoes

16 and 18 as the flywheel rotates in its counterclockwise direction. The area of the terminal faces 32b, and 32c, and 34b of the three magnetic elements and also the peripheral spacing between them is carefully controlled so that the magnetic field created by the

pole shoes

16 and 18 as the flywheel rotates and passes the pole shoes past the terminal faces of the three magnetic elements generates the voltages desired in the

coils

32 and 34 in a specific timed relation to the rotation of the engine whereby the desired effect is attained in the ignition circuit shown in FIG. 6.

It will be noted that during the counterclockwise rotation of the flywheel 10, the leading pole shoe 16 first passes the terminal face 34b of the coil 34, then the terminal face 32c, and then the last terminal face 32b. The

faces

32c and 32b are magnetically related to coil 32. Of particular importance is the peripheral spacing between

faces

34b and 320 as related to the peripheral area of the pole shoe 16. The spacing is such that the magnetic flux active in the pole shoe 16 is controlled by a division of flux between the

faces

34b and 32c when the shoe 16 covers both, whereby a single positive trigger pulse is generated in coil 34 which has two distinct positive peaks with different timing relations. This is clearly shown in FIG. where the conditions of flux and voltages generated in

coils

34 and 32 are shown. The vertical dotted lines A, B, C, D and E, are related to the angular position of the

faces

32b, 32c, 34b, and the

pole shoes

16 and 18, the important angular positions being between B and C, at which time the voltages in the coil 34 control the gate G of the switch SCR to unload the charge on the capacitor CD through the primary P of the high tension coil C to cause a high voltage in the secondary S to tire the spark plug SP.

Referring specifically now first to FIG. 1, then successively to FIGS. 2, 3 and 4, a normal cycle of operation at starting of the engine will be described. It will be noted that the air gap 20 between the

pole shoes

16 and 18 is just beginning to cooperate with the pole face 32b so that the rate of change of the magnetic flux in the coil 32 is at maximum and a positive voltage pulse will be generated in coil 32 which will pass diode D to charge the capacitor CD. Any negative pulse created at any time in the coil 32 will be loaded by diode D and resistance R in series circuit therewith. Thereafter the flywheel will continue to rotate in a counterclockwise direction for about 300 to attain the position of the flywheel shown in FIG. 2.

The pole shoe 16 in FIG. 2 has already covered face 34b so that the flux density will be about a maximum, but as it begins to cooperate at point X with the face 32c, the flux will divide between both

faces

34b and 320, to substantially reduce the flux density in the face 34b, whereby a reduced rate of change of flux for trigger coil 34 is brought about, which reduces the voltage generated therein to produce a secondary peak Y in its voltage curve in advance of the principal voltage peak Z, which occurs when the air gap 20 between the

pole shoes

16 and 18 traverses the face 34b (FIG. 3) to create the maximum rate of change of flux in. the coil 34 and its principal voltage pulse Z as shown in solid lines in the second curve from the top of FIG. 5. When the engine is starting and rotating at low speed, the voltage peak Y is too low in value to gate the switch SCR and nothing happens in the ignition circuit, but when the voltage peak Z occurs, its voltage is sufficiently high to gate the switch SCR which becomes conductive and discharges the capacitor CD through the primary P to cause the secondary S to fire the spark plug SP. The'diode D conducts alternately with the switch SCR and conducts the ringing current of the primary P.

In FIGS. 4 and l, the

pole shoes

16 and 18 cooperate in an effective manner only with

pole faces

32c and 32b and create a charging current for the capacitor CD in the coil 32 preparatory to a new cycle of operation. The flux changes which create negative voltages are dampened by diode D and may be disregarded.

After the engine starts and the speed of rotation of the flywheel 10 increases to a predetermined speed as controlled by variable resistor VR (FIG. 6), the voltages of peaks Y and z are raised substantially to new values Y and Z as shown in dotted lines in curve II of FIG. 5. It will be noted that at starting the principal peak Z had suificient voltage value to gate the switch SCR while secondary advanced peak Y did not. The trigger level of the switch SCR is shown by a horizontal line. The firing of the spark plug SP was therefore at a later or retarded position at point R. With the starting of the engine and the predetermined increased speed, the trigger level of the switch SCR is attained much earlier at point L on the secondary peak Y, which substantially advance the firing of the spark plug SP to compensate for the higher speed of operation of the engme.

The additional resistors R and R and the negative temperature thermistor R are provided for temperature compensation for the trigger circuit of the switch SCR. As pointed out before, resistor VR in series circuit with the coil 3, diode D and resistor R to gate G of the switch SCR is used for the purpose of controlling the predetermined speed of rotation of the engine at which the ignition advance will become effective. Diode D will prevent reverse voltage from effecting the action of the switch SCR.

Referring now to FIG. 7, a schematic diagram of connection for the ignition circuit is shown incorporating an alternate method of temperature compensation. The thermistor R and the diode D shown in FIG. 6 are elminated resulting in a more economical and simpler construction of the device. In FIG. 7, the trigger coil 34 is wound for instance, with wire made of a nickel alloy so as to have a positive temperature coefficient. To compensate for the higher resistance of the nickel alloy wire as compared to copper wire, a bifilar winding of two nickel wires in parallel is preferred, but due to the paramagnetic state of the nickel alloy wire, only one fourth the number of turns are required to attain the desired voltage values for gating the switch SCR.

On reverse operation of the engine with the flywheel 10 rotating in a clockwise direction as shown in FIGS. 1-4, the switch SCR in FIGS. 6 and 7 will be gated to a high conductance state at time M in FIG. 8. The charging winding current will reduce at an exponential rate from time N to time P. The current at time P at a predetermined flywheel speed will be at a sufficient level to exceed the holding current of the SCR which will result in the SCR being in-its high conductance state from time M to time P. Therefore there will be no charge in the ignition capacitor above the predetermined flywheel speeds in the clockwise direction which results in no ignition output.

It is to be understood that the above detailed description of the present invention is intended to disclose an embodiment thereof to those skilled in the art, but that the invention is not to be construed as limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawing since the invention is capable of being practiced and carried out in various ways without departing from the spirit of the invention. The language used in the specification relating to the operation and function of the elements of the invention is employed for purposes of description and not of limitation, and it is not intended to limit the scope of the following claims beyond the requirements of the prior art.

We claim:

1. In a capacitor discharge ignition system for an internal combustion engine wherein a controlled rectifier is periodically triggered to discharge a capacitor through the primary winding of an ignition coil, a generating and control device for periodically charging said capacitor and triggering said controlled rectifier comprising, in combination, a rotor and a stator, means for driving said rotor in synchronism with the engine, a permanent magnet mounted on said rotor and including pole shoes, a charging coil having a magnetic core, means mounting said charging coil on said stator with ends of said charging coil core positioned for excitation by said pole shoes, means for charging the capacitor from said charging coil, a trigger coil having a magnetic core, means mounting said trigger coil on said stator with an end of said trigger coil core positioned for excitation by said pole shoes in advance of excitation of said charging coil core, said trigger coil core end being spaced from a leading one of said charging coil core ends by a distance less than the width of the leading one of said pole shoes whereby a single positive voltage pulse having spaced peaks of different voltage values is generated in said trigger coil when said pole shoes are rotated past said trigger coil core, the lower voltage peak being first in point of time and below a predetermined level lower than the higher voltage peak during starting of the engine and above such predetermined level after the engine has started, and means responsive to such positive pulse exceeding such predetermined level for triggering the controlled rectifier.

2. A generating and control device for a capacitor discharge ignition system, as defined in claim 1, and including means for preventing charging of said capacitor when said rotor is rotated in a reverse direction.

3. A generating and control device for a capacitor discharge ignition system, as defined in claim 1, wherein said charging coil core is substantially U- shaped having leading and lagging ends positioned for excitation by said pole shoes, and wherein said charging coil is mounted on said core adjacent said lagging end.

Claims

3. A generating and control device for a capacitor discharge ignition system, as defined in claim 1, wherein said charging coil core is substantially U-shaped having leading and lagging ends positioned for excitation by said pole shoes, and wherein said charging coil is mounted on said core adjacent said lagging end.