US3704397A

US3704397A - Ignition adapter circuit

Info

Publication number: US3704397A
Application number: US207261A
Authority: US
Inventors: Thomas J Crouch; George E Gynn
Original assignee: Syncro Corp
Current assignee: Syncro Corp
Priority date: 1971-12-13
Filing date: 1971-12-13
Publication date: 1972-11-28
Anticipated expiration: 1989-11-28
Also published as: CA960295A

Abstract

An electrical ignition system for adapting a conventional magneto spark ignition system to a capacitor discharge ignition system.

Description

1 I IG ITION ADAPTER cmcurr I SUMMARY BACKGROUND OF THE INVENTION The present invention relates tocapacitor discharge ignition systems and more particularly toan electrical ignition ,systemfor adapting a conventional magneto spark ignition system to a capacitor discharge ignition system. i

CDIsystems have many advantages over the conven tional spark ignition system and in many existing engine installations, such as snowmobiles having engines with flywheel magnetos, in which spark ignition systems are already installed it would be desirable to convert those systems to CD1 systems. The present invention is directed to such a conversion system in which a'conventional' spark ignition system can be easily and inexpensively converted to a CDI system. I

In the'present invention the conversion to a CD1 system can be madewithout the need for disassembling the engine flywheel. 'Also the presentinvention .is directed to conversion of a two cylinder two cycle en? gine having a magneto withan ignition winding and a set of points for each cylinder; in this system the'points are used to' tire or trigger the occurrence of ignition. Therefore it is an object of the present invention to provide a conversion system by which a conventional spark ignition system can be economically and'simp'ly converted to a CD1 system. It is another object to provide a conversion system of theabove described type in which the points are used to provide the trigger to initiate ignition. It is another general object of the present invention to provide a novel conversion system for. converting a conventional spark ignition system to a GM system.

Other objects, features, and advantages of the present invention will become apparent-from the subsequent description and the appended claims, taken in conjunctionwith the accompanying drawing, in which acircuit diagram depicting the ignition adapter system of the present invention is shown. i

In the drawing a portion of a conventionalmagneto ignition system is generally indicated by the numeral 10 and an Ignition Coil and Plug Section for use with the Magneto Portion ll) is generally indicated by the numeral 12. For a conventional magneto spark ignition system the Magneto Ignition Portion 10 would be'connected directly with the Ignition Coil and Plug Section 12. In the present invention that system is converted into a Cl)! system by the use of the CDI Adapter Portion 14.

The Magneto Ignition Portion 10 includes a pair of circumferentially displaced magneto coils La and Lb which are secured to a stator 14 which is fixed under a flywheel 16. The flywheel is provided with a pair of permanent magnets 18 which are circumferentially spaced and which are of opposite polarities, radially. Capaci tors Ca and Cb are connected across windings La and Lb, respectively, with one end of the capacitors and windings being connected to ground. The capacitors Ca and Cb are conventionally provided to minimize arcing across points Pa and Pb, respectively. Points Pa and Pb each have one contact connected to the associated capacitor Ca, Cb and another contact connected to ground. In the conventional existing system (to which Adapter Portion 14 applies) the Magneto Ignition Portion just described was connected directly to thelgnition Coil and Plug Section 12.

The Section 12 includes ignition coils ICa andlCb each having secondary windings connected across the electrodes of spark plugs Sa and Sb, respectively. In the existing circuit, then, the primary winding of coil ICa was connected directly to the ungrounded contact of points Pb (via a conductor indicated in dotted lines as 20a) and the primary winding of coil lCb was connected directly to the ungrounded contact of points Pa (via a'conductor indicated in dotted lines as 20b). Thus in the pre-existing circuit the electrical energy of magneto winding La was transmitted to and used by coil lCb to fire plug Sb and the electrical energy of winding Lb was transmitted to and used by coil ICa to fire plug 80. This arrangement is reversed inthe adapter of the' present invention for reasons to be seen.

The CDlAdapter Portion 14 includes a capacitor CDa which is electrically connected to the primary of coil lCa'via conductor 22a'and toltheungrounded contact of points Pa via conductor 24a, a charging diode Dla and conductorifiaeA diode D2a is reverse connected from conductor 26a to ground to provide. a'path for high voltage-transients and also for negative potentials. A silicon controlled rectifier, SCRa, is connected to control the discharge of capacitor CDa into the primary of coil ICa. SCRa has its anode connected to conductor 24a and its cathode grounded. The gate of SCRa is connected to be triggered in a manner to be described. Thus capacitor CDa will be charged, when points Pa are opened from magneto windingLa via conductor 26a, diode Dla and conductor Ma. At this time SCRa is not in conduction. Subsequently, SClRa is triggered to conduct and the charge on CDa can then flow to the primary of ICa to fire the plug Sa. One diffficulty with (EDI-adapter systems is to find a direct, economical way to time the firing, i.e. via the discharge of the capacitor CDa. in the present invention this is done in a simple manner by providing the timing via the other set of points (Pb) and voltage generated by the other magneto winding (Lb).

Thus in the Adapter Portion M the gate of SCRa is connected to the points Pb and winding Lb via a blocking diode 133a and resistor Ra connected to conduct0r'26b. A diode D2b is reverse connected from conductor 26b to .ground. Conductor 26b is also connected to capacitor CDb via charge diode Dlband conductor Mb. Capacitor CDb is connected to the primary of ignition coil ICb via conductor 22b. A silicon controlled rectifier, SCRb, has its anode connected to conductor 24b and its cathode grounded. The gate of SCRb is connected to the points Pa and magneto winding La via resistor Rb, blocking diode 133b, and conductor 26a. Capacitor CDb will be charged, when points Pb are opened, from magneto winding Lb via conductor 26b, diode Dlb and conductor 24b. At this time SCRb is not in conduction. Subsequently SCRb is triggered to conduct and the charge in CDb will fire lCb. Note that points Pa and Pb are located approximately apart and are normally closed and will be opened approximately 180 apart via a cam (generally indicated as ZS) rotatable with the flywheel 16. When points Pa are opened (points Pb being closed) by cam 2b the voltage generated by winding La will quickly charge capacitor CDa; at the same time the voltage at La will trigger SCRb to discharge CDb and fire Sb. Subsequently when points Pb are opened (points Pa now being closed) by cam 28 the voltage generated by winding Lb will curred when the Magneto Ignition Portion was conventionally connected directly to the Ignition Coil and Plug Section 12. The timing is still provided by the flywheel 16 as it actuates the points Pa and Pb. Since the flywheel 16 is connected directly to the engine crankshaft 17, the proper timing, relative to the position of the pistons, is provided. Since the non-rotatable components of Magneto Ignition Portion 10 are conventionally located under the flywheel 16 this means that the system of thepresent invention can be utilized without disturbing the flywheel by merely disposing the Adapter Portion between conductors 26a, 26b, 22a and 22b. Preferably the ignition coils lCa and ICb are high rise time coils, i.e. having a rise time of around two microseconds. v

While it willbe apparent that the preferred embodiment of the invention disclosed is well calculated to fulfill the objects above stated, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope or fair meaning of the invention.

What is claimed is:

1. An adapter assembly for converting an existin magneto ignition system to a capacitor discharge ignition system with the magneto having a rotor and a stator'and having a first magneto coil for providing an alternating output potential and connected to and across a first set of breaker points and having a second magneto coil forproviding an alternating output potential and connected to and across a second set of breaker points with the first and second magneto coils and first and second sets of points being supported on the stator, a first conductor normally connecting the first magneto coil and first set of points to a first ignition coil, a second conductor normally connecting the second i magneto coil and second set of points to a second ignition coil, said adapter assembly comprising: a first capacitor, first charge circuit means connecting the first conductor and hence the first magneto coil to said first capacitor for charging said first capacitor with the electrical energy of the output potential from the first magneto coil, firstdischarge circuit means connecting said first capacitor to the second ignition coil for transmitting the stored electrical energy in said first capacitor in response to the occurrence of a first preselected positional relationship between the rotor and the stator, a second capacitor, second charge circuit means connecting the second conductor and hence the second magneto coil to said second capacitor for charging said second capacitor with electrical energy of the output potential from the second magneto coil, second discharge circuit means connecting said second capaci tor to the first ignition coil for transmitting the stored electrical energy in said second capacitor in response to the occurrence of a second preselected positional relationship between the rotor and the stator.

2. The adapter assembly of claim 1 in which said first discharge circuit means includes first solid state switch means for transmitting the stored electrical energy from said first capacitor in response to a first trigger pulse and includes first trigger means operable in response to actuation of the second breaker points for providing said first trigger pulse, said second discharge circuit means includes'second solid state switch means for transmitting the stored electrical energy from said second capacitor in response to a second trigger pulse and includes second trigger means operable in response to actuation of the first breaker points for providing said second trigger pulse.

3. Theadapter assembly of claim 2 with said first charge circuit means including the first breaker points with said first capacitor being charged from the first magneto coil when the first breaker points are in open circuit condition, said second charge circuit means including the second breaker points with said second capacitor being charged from the second magneto coil with the second breaker points are in open circuit con dition, said first trigger means providing said first trigger pulse with the second breaker points in open circuit condition, said second trigger means providing said second trigger pulse with the first breaker points in open circuit condition.

4. An adapter assembly for converting an existing magneto spark ignition system to a capacitor discharge ignition systemwith the magneto having a rotor and a stator and having at least one magneto coil connected to the stator for providing an alternating output potential and at least one set of breaker points in combination with a spark ignition coil, said adapter assembly comprising: a capacitor, first circuit means connecting the magneto coil to said capacitor for charging said capacitor directly with the electrical energy of the output potential from the magneto coil for only one polarity of the output potential, second circuit means connecting said capacitor to .the ignition coil, said second circuit means comprising: solid state switch means having a pair of principal electrodes and a gate electrode for transmitting the stored energy on said capacitor to the ignition coil via said principal electrodes upon the occurrence of a trigger pulse at said gate electrode, and trigger means operatively connected with the rotor for providing said trigger pulse in response to the occurrence of a preselected positional relationship between the rotor and the stator.

5. The adapter assembly of claim 4 for use with the existing magneto spark ignition system further including a second set of breaker points, said trigger means including the second set of breaker points and providing said trigger pulse in response to actuation of the second set of breaker points.

6. The adapter assembly of claim 5 with said first circuit means including the first set of breaker points for charging said capacitor with the first set of breaker points in an open circuit condition, said trigger means providing said trigger pulse in response to the second set of breaker points being in an open circuit condition.

Claims

1. An adapter assembly for converting an existing magneto ignition system to a capacitor discharge ignition system with the magneto having a rotor and a stator and having a first magneto coil for providing an alternating output potential and connected to and across a first set of breaker points and having a second magneto coil for providing an alternating output potential and connected to and across a second set of breaker points with the first and second magneto coils and first and second sets of points being supported on the stator, a first conductor normally connecting the first magneto coil and first set of points to a first ignition coil, a second conductor normally connecting the second magneto coil and second set of points to a second ignition coil, said adapter assembly comprising: a first capacitor, first charge circuit means connecting the first conductor and hence the first magneto coil to said first capacitor for charging said first capacitor with the electrical energy of the output potential from the first magneto coil, first discharge circuit means connecting said first capacitor to the second ignition coil for transmitting the stored electrical energy in said first capacitor in response to the occurrence of a first preselected positional relationship between the rotor and the stator, a second capacitor, second charge circuit means connecting the second conductor and hence the second magneto coil to said second capacitor for charging said second capacitor with electrical energy of the output potential from the second magneto coil, second discharge circuit means connecting said second capacitor to the first ignition coil for transmitting the stored electrical energy in said second capacitor in response to the occurrence of a second preselected positional relationship between the rotor and the stator.

2. The adapter assembly of claim 1 in which said first discharge circuit means includes first solid state switch means for transmitting the stored electrical energy from said first capacitor in response to a first trigger pulse and includes first trigger meAns operable in response to actuation of the second breaker points for providing said first trigger pulse, said second discharge circuit means includes second solid state switch means for transmitting the stored electrical energy from said second capacitor in response to a second trigger pulse and includes second trigger means operable in response to actuation of the first breaker points for providing said second trigger pulse.

3. The adapter assembly of claim 2 with said first charge circuit means including the first breaker points with said first capacitor being charged from the first magneto coil when the first breaker points are in open circuit condition, said second charge circuit means including the second breaker points with said second capacitor being charged from the second magneto coil with the second breaker points are in open circuit condition, said first trigger means providing said first trigger pulse with the second breaker points in open circuit condition, said second trigger means providing said second trigger pulse with the first breaker points in open circuit condition.

4. An adapter assembly for converting an existing magneto spark ignition system to a capacitor discharge ignition system with the magneto having a rotor and a stator and having at least one magneto coil connected to the stator for providing an alternating output potential and at least one set of breaker points in combination with a spark ignition coil, said adapter assembly comprising: a capacitor, first circuit means connecting the magneto coil to said capacitor for charging said capacitor directly with the electrical energy of the output potential from the magneto coil for only one polarity of the output potential, second circuit means connecting said capacitor to the ignition coil, said second circuit means comprising: solid state switch means having a pair of principal electrodes and a gate electrode for transmitting the stored energy on said capacitor to the ignition coil via said principal electrodes upon the occurrence of a trigger pulse at said gate electrode, and trigger means operatively connected with the rotor for providing said trigger pulse in response to the occurrence of a preselected positional relationship between the rotor and the stator.