US3911887A

US3911887A - Capacitor discharge ignition system

Info

Publication number: US3911887A
Application number: US443839A
Authority: US
Inventors: Bob O Burson
Original assignee: Phelon Co Inc
Current assignee: RE Phelon Co Inc
Priority date: 1974-02-19
Filing date: 1974-02-19
Publication date: 1975-10-14
Anticipated expiration: 1992-10-14
Also published as: IT1020696B; DE2436095A1; JPS50113640A

Abstract

In a capacitor discharge ignition system for an internal combustion engine, discharge of the capacitor through the primary winding of an ignition transformer is controlled by a silicon controlled rectifier. Trigger signals for triggering the SCR are produced by a trigger coil mounted on one pole of a ferromagnetic core located adjacent the path of a rotating permanent magnet. The ignition transformer primary and secondary coils are mounted on the same pole of the ferromagnetic core as the trigger coil, and all three coils are contained and potted within a common housing to form a compact module.

Description

United States Patent 1 [111 3,911,887

Burson Oct. 14, 1975 CAPACITOR DISCHARGE IGNITION [75] Inventor: Bob 0. Burson, East bongmeadow,

Mass.

[73] Assignee: R. E. Phelon Company, Inc., East Longmeadow, Mass.

[22] Filed: Feb. 19, 1974 [21] App]. No.2 443,839

[52] US. Cl 123/148 R [51] Int. Cl. F021 3/06 [58] Field of Search ..123/148\E, 148 OCD,

123/148 MCD [56] References Cited H UNITED STATES PATENTS 3,367,314 2/1968 Hirosawa et a1. 123/148 E 3,447,521 6/1969 Piteo 123/148 E 3,465,739 9/1969 Burson 123/148 E 3,500,809 3/1970 Hohne et a1 123/148 E SYSTEM Primary Examiner-Wendell E. Burns Assistant Examiner.lames W. Cranson, Jr. Attorney, Agent, or FirmMcCormick, Paulding & Huber ABSTRACT In a capacitor discharge ignition system for an internal combustion engine, discharge of the capacitor through the primary winding of an ignition transformer is controlled by a silicon controlled rectifier. Trigger signals for triggering the SCR are produced by a trigger coil mounted on one pole of a ferromagnetic core located adjacent the path of a rotating permanent magnet. The ignition transformer primary and secondary coils are mounted on the same pole of the ferromagnetic core as the trigger coil, and all three coils are contained and potted within a common housing to form a compact module.

6 Claims, 3 Drawing Figures U.S. Patent 0m. 14, 1975 FIG. 3

1 CAPACITOR DISCHARGE IGNITION SYSTEM BACKGROUND OF-THE INVENTION This invention relates to ignition systems for use with spark ignited internal combustion engines, and deals more particularly with an improved capacitor discharge ignition system.

Various different types of ignition systems have been proposed in the past for supplying high voltage electrical power to the spark plug or plugs of a spark-ignited engine for producing the spark necessary to sustain engine operation. At present, one general type of ignition system in relatively wide use is the capacitor discharge ignition system wherein, during each cycle of operation of the system, a capacitor is first charged from a suitable voltage source and then at the proper instant is discharged through the primary winding of a voltage stepup ignition transformer to produce across the transformer secondary winding a high voltage used to fire an associated spark plug. Examples of capacitor discharge ignition systems are shown by my previous US. Pat. Nos. 3,465,739; 3,508,116; 3,534,722; and 3,619,634. As is evident from these patents, it is known to use a triggered gate element, such as a silicon controlled rectifier, to control the discharge of the capacitor through the transformer and to trigger such gate element by a trigger signal induced in a separate trigger coil.

The purpose of this invention is to reduce the space requirements, complexity and cost of capacitor discharge ignition systems while improving reliability and other performance characteristics. This purpose is achieved by an arrangement wherein the trigger coil and the primary and secondary coils of the ignition transformer are all three contained in a single module which is preassembled and adapted to be readily fitted onto a pole of a ferromagnetic core which cooperates with a rotating permanent magnet to induce trigger signal voltages in the trigger coil. In particular, the aforementioned module, in addition to the three coils, consists of a plastic housing within which the three coils are potted by a suitable potting agent. The housing includes a central chimney or tubular portion adapted to receive the pole onto which the module is fitted and the three coils surround this chimney or tubular portion. The general shape and size of the module is similar to that of transformer modules often used in the past in magneto ignition systems, thereby enabling the ignition system of this invention to be used in substantially the same environments as previous magneto ignition systems, especially in situations where most of the components of the ignition system are located within the rim of a flywheel carrying one or more permanent magnets or permanent magnet assemblies.

SUMMARY OF THE INVENTION This invention resides in a capacitor discharge ignition system for supplying high voltage power at proper times to the spark plug or plugs of a spark-ignited internal combustion engine. The system includes a capacitor, a means for charging the capacitor, and a voltage step-up ignition transformer having a secondary winding adapted to be connected to the spark plug or plugs of the associated engine. A circuit for discharging the capacitor through the primary winding of the transformer is also provided and includes a triggered gate element, such as an SCR, which is normally nonconducting to prevent the discharge of the capacitor through the primary winding and which is triggered to a conducting state by a trigger signal applied to its trigger terminal to permit the discharge of the capacitor through the primary winding. A trigger signal for triggering the gate element is provided by a trigger coil cooperating with a permanent magnet rotated in synchronism with the operation of the engine. The trigger coil is mounted on a core of ferromagnetic material located adjacent the path of the magnet and having a pole which receives the trigger coil and through which a pulse of flux from the magnet passes each time the magnet is moved past the pole in the course of its rotation. The primary coil and secondary coil of the transformer are also both mounted on the aforesaid pole along with the trigger coil, and preferably all three coils are contained in a common housing to form a single module readily slipped onto the pole in the assembly of the system. The rotating magnet may be part of a magnet assembly carried by the rim of a flywheel forming part of the engine and the ferromagnetic core may be part of a stator located within such flywheel rim. The magnet may also be used to generate a voltage in another generating coil for charging thecapa'citor. This generating coil may be provided as an additional module adapted for reception on another pole and such other pole may be either part of another ferromagnetic core separate from the one carrying said first module or part of the same core carrying the first module.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view showing parts of a capacitor discharge ignition system embodying this invention, part of the rim of the flywheel rotor being shown broken away to reveal the permanent magnet assembly.

FIG. 2 is a schematic wiring diagram of a capacitor discharge ignition system embodying this invention and utilizing the parts of FIG. 1.

FIG. 3 is a sectional view taken through the trigger coil and transformer module of FIG. 1. i

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Turning to the drawings, and first considering FIG. 1, major components of a capacitor discharge ignition system embodying this invention are there shown and comprise a stator assembly 10 and a rotatable member 12. The stator assembly 10 is adapted to be attached to the block or other stationary structure of an associated engine and contains an opening 14 for accommodating a shaft, usually the crankshaft, of the engine which is rotated in synchronism with the engine operation. The rotatable member 12 is adapted to be fixed to the shaft which passes through the stator opening 14, and in the illustrated case constitutes a flywheel having an annular rim l6 surrounding the stator assembly 10. A web portion 18 extends from a central or hub portion 20 to the rim l6 and with the rim forms a chamber for receiving the stator assembly. In FIG. 1, the view presented is one taken looking away from the engine and the web portion 18 of the flywheel is behind the stator assembly 10.

The rotatable member or flywheel 12 serves as a flywheel for the associated engine and, in addition, carries in its rim 16 a permanent magnet assembly 22 forming part of the ignition system. This assembly includes a permanent magnet 24 having magnetic poles of opposite polarity at its opposite ends circumferentially of the rim, and two

pole pieces

26, 26 of ferromagnetic material, such as laminated iron, each engaging one of the ends of the magnet 24 and providing a circumferentially extending pole face 28 on the interior surface of the rim 16.

The stator assembly includes a mounting plate 30 and two

ferromagnetic cores

32 and 34 fixed to the mounting plate. The two

cores

32 and 34 are generally similar to one another and are preferably made of laminated iron. The core 32 has three radially extending and angularly spaced

poles

36, 38 and 40. Likewise, the core 34 has three radially extending and angularly spaced

poles

42, 44 and 46. Each of the

poles

36, 38, 40, 42, 44 and 46 has on its outer end a radially outwardly directed face for cooperation with the

pole faces

28, 28 of the magnet assembly 22. As will be appreciated by those skilled in the art, the arrangement and spacing of the three poles of each core and of the spacing of the permanent magnet pole faces 28, 28 is such that as the magnet assembly 22 passes each core, a pulse of flux from the magnet passes through the

center pole

38 or 44 of such core. That is, as the magnet assembly passes a core, the magnetic flux which passes through the

center pole

38 or 44 of the core first builds up, from zero, relatively gradually on one side of the zero axis, it then very rapidly changes to the opposite side of the zero axis, and then it gradually returns to zero. Mounted on the center pole 38 of the core 32 is a generating coil and component module 48. Mounted on the center pole 44 of the core 34 is a trigger coil and transformer module 50.

As will be appreciated by the following discussion of FIG. 2, the mechanism shown in FIG. 1 is a compact unit comprising substantially the entire ignition system for the associated engine. The only connections required to complete the ignition system are provided by two

conductors

52 and 54. The conductor 54 is for connection to a shut-off switch 53 (FIG. 2) and the conductor 54 is a high tension lead for connection to the spark plug 82 (FIG. 2) of the engine. In addition to the two

conductors

52 and 54, each

module

48 and 50 has three

conductors

56, 58 and 60 extending therefrom and connected to corresponding conductors of the opposite module.

Turning to FIG. 2, the components of an ignition system utilizing the unit of FIG. 1 are there shown in schematic form. The module 48 includes a generating winding 62 which surrounds the pole 38 of FIG. 1, a capacitor 64, a silicon controlled rectifier 66,

resistors

68 and 70 and diodes 72 and 74. These components are preferably contained within a common plastic housing and potted in the housing by a potting agent. The housing may be generally similar to that used for the module 50, as disclosed in FIG. 3 and discussed in more detail hereinafter.

The electrical connection of the components of the module 48 is such as shown by FIG. 2. In particular, the capacitor 64 is connected across the generating coil 62 in cooperation with the diodes 72 and 74. The diode 72 which is connected in parallel with the generating coil 62, assures that only positive portions of the voltage waveform induced in the coil are conducted to the capacitor, and the diode 74 connected in series with the generating coil prevents the charge on the capacitor from returning to the generating coil during the negative portion of each induced waveform in the generating coil.

The resistor 68 is connected to the gate or trigger terminal of the SCR 66 and serves to limit the flow of current through the trigger terminal. The resistor is not essential to the normal operation of the ignition system and may be eliminated, if desired. It is, however, a safety measure for preventing unintended starting of the engine after shut down. That is, the resistor 70 is one of relatively high value which slowly bleeds the charge from the condenser 64 after shut down should the capacitor be in a charged state at shut down. Therefore, the engine cannot again be started unless the flywheel is rotated a sufficient amount to move the permanent magnet assembly past both the generating coil module and the trigger coil and transformer coil module. For example, assume that the engine in question is used in a rotary lawn mower and that after the engine is stopped, the user in inspecting the blade moves the blade slightly and thereby slightly turns over the engine and slightly rotates its flywheel. If this movement occurs when the permanent magnet assembly is in the vicinity of the trigger coil module, a trigger signal may be generated which might fire the engine and create a hazardous situation for the user, if the capacitor is charged at the time the trigger signal is generated. Having the capacitor discharged by the resistor 70 prevents such an occurrence.

Considering the trigger coil and transformer module 50 as shown in FIG. 2, this module includes three separate coils all three of which surround the pole 44 of FIG. 1. One coil 76 is a trigger coil connected to the gate terminal of the SCR 66 through the resistor 68. The other two coils, are respectively, the primary winding 78 and secondary winding 80 of a voltage step-up ignition transformer 79, the secondary winding 80 being adopted for connection to the spark plug 82 of the engine through the high tension lead 54. The dots associated with the three

coils

76, 78 and 80 indicate ends of the coils having a common polarity with respect to voltages induced therein by changes in the magnetic flux passing through the pole 44.

The actual construction of the trigger coil and transformer module 50 is shown in greater detail in FIG. 3. As there shown, the module 50 includes a plastic housing 84 having a central tubular portion or chimney 86 sized and shaped to receive the pole 44. Immediately adjacent and surrounding the chimney portion 86 is the trigger coil 76, shown in FIG. 3 to comprise two layers of windings. On top of the trigger coil 76 is the primary winding 78 of the transformer, also comprising two layers of windings. One end of the trigger coil 76 is connected to the conductor 58. The other end of the trigger coil is connected to both one end of the primary winding 78 and the conductor 56 by a connector indicated at 88. The other end of the primary winding 78 is connected to the ground conductor 60 and to one end. of the secondary winding 80 by a connector indicated at 83. The secondary winding 80 surrounds the trigger coil and primary winding and has its other, high tension, end connected to a tack 88 located at the inner end of a socket 90 formed in the housing 84 and adapted to receive the associated end of the high tension lead 54.

In the operation of the system shown in FIGS. 1 and 2, as the engine runs, the flywheel 12 rotates in the direction of the arrow of FIG. 1 in synchronism with the operation of the engine, and the magnet assembly 24 is thereby alternately swept past the two

stator cores

32 and 34 respectively carrying the two

modules

48 and 50. In a given cycle of operation, the magnet assembly 24 first moves past the stator core 32 carrying the generating coil module 48 and induces a voltage in the generating coil 62 which charges the capacitor 64 to a relatively high voltage level. Thereafter, the magnet assembly moves past the stator core 34 carrying the trigger coil and transformer module 50. This latter movement causes a pulse of magnetic flux to pass through the center pole 44 which induces a trigger voltage signal in the trigger coil 76 and triggers the SCR 66 to a conducting state, thereby discharging the capacitor 64 through the primary winding 78. This sudden discharge of the capacitor through the primary winding 78-in turn induces a high voltage across the ends of the secondary winding 80 which high voltage is applied to the spark plug 82 to create a spark across its gap.

The mounting of the module 50 on the pole 44, it should be noted, makes a double usage of the pole material. First, the pole 44 serves, in cooperation with the magnet assembly 22, as part of a mechanism for creating a rapid change of magnetic flux through the trigger coil to induce a trigger signal in such coil. Second, the pole 44 acts as a core for the primary and

secondary windings

78 and 80 to enhance the inductive coupling between said two coils in the same fashion as does the core used in more conventional ignition transformers.

A still further advantage is achieved from the placement of the trigger coil, the primary coil and the secondary coil all on the same pole 44. At the instant the SCR 66 is triggered to discharge the capacitor 64, the voltage induced in the primary coil 78 by the magnetic flux from the magnet assembly 22 opposes the voltage across the capacitor. This means that at the instant in question, the flux passing through the transformer coils is opposite to the flux therethrough generated by the capacitor discharge. This situation is essentially beneficial as it makes more efficient use of the ferromagnetic material of the pole 44 and produces a greater flux change, and consequently a higher secondary voltage then would be the case if no changing magnetic flux were passing through the transformer coils at the instant of condenser discharge.

It will, of course, be understood that various changes and modifications may be made from the specific embodiment of the invention illustrated and described above without departing from the broader aspects of the invention. For example, in the illustrated embodiment, the two

modules

48 and 50 are shown to be each mounted on a separate one of two three-pole cores. This is not essential, however, and if desired, the two modules could be mounted on different poles of a single core. Also, the number of poles on a core is not critical, it being required only that the generating coil module 48 be mounted on one pole and the trigger coil and transformer module be mounted on another pole in which poles flux pulses are successively created by a rotating magnet assembly. Still further, it is not essential to the broader aspects of the invention that the capacitor be charged by a generating coil excited by the same magnet as used to excite the trigger coil, and various other means may be used to supply charging energy to the capacitor.

1 claim:

1. A capacitor discharge ignition system for use with a spark ignited internal combustion engine, said system comprising: a capacitor, means for charging said capacitor, a voltage step-up ignition transformer having a primary coil and a secondary coil, a circuit for the discharge of said capacitor through said primary coil, said circuit including a triggered gate element having a trigger terminal, said triggered gate element being one which is normally non-conducting so as to prevent the discharge of said capacitor through said primary coil and which is triggered to a conducting state by a trigger signal applied to its trigger terminal to permit the discharge of said capacitor through said primary coil, a permanent magnet means adapted for rotation in synchronism with the operation of the engine with which said system is used, a first core of magnetic material located adjacent the path of said magnet means and having a first pole through which a pulse of fiux from said magnet means passes each time said magnet means is moved past said pole in the course of its rotation, and a trigger coil mounted on said pole and connected with said trigger terminal of said triggered gate element for triggering said triggered gate element to its conducting state by the voltage induced in said trigger coil by said flux pulse, said primary coil and secondary coil also both being mounted on said pole along with said trigger coil.

2. A capacitor discharge ignition system as defined in claim 1 further characterized by a housing surrounding said pole, said trigger coil, said primary coil and said secondary coil all being received within said housing.

3. A capacitor discharge ignition system as defined in claim 1 further characterized by said means for charging said capacitor comprising a generating coil, means for exciting said generating coil by the magnetic flux from said permanent magnet means to induce a voltage waveform therein as said permanent magnet means traverses a given portion of its path of movement, and means connecting said generating coil with said capacitor to cause such voltage waveform to charge said capacitor.

4. A capacitor discharge ignition system as defined in claim 3 further characterized by said means for exciting said generating coil including a second pole of magnetic material around which said generating coil is received.

5. A capacitor discharge ignition system as defined in claim 4 further characterized by a second core of magnetic material separate from said first core and located adjacent the path of said magnet means, said second pole being part of said second core of magnetic material.

6. A capacitor discharge ignition system for use with a spark ignited internal combustion engine, said ignition system comprising a capacitor in which electrical energy may be temporarily stored for subsequent use in creating a spark, a permanent magnet adapted for rotation in synchronism with the operation of said engine, a core of magnetic material located adjacent the path of said magnet and having a pole through which a pulse of flux from the magnet passes each time the magnet is moved past said pole in the course of its rotation, a coil module mounted on said pole, said coil module including a housing and also including a trigger coil, a primary coil and a secondary coil, all three of which coils are located within said housing and surround said pole, a triggered gate element having an anode terminal, a cathode terminal and a trigger terminal, a first circuit connecting said capacitor in series with said primary coil through said anode and cathode terminals of said triggered gate element, and a second circuit connecting said trigger coil between said cathode terminal and said trigger terminal of said triggered gate element.

Claims

1. A capacitor discharge ignition system for use with a spark ignited internal combustion engine, said system comprising: a capacitor, means for charging said capacitor, a voltage step-up ignition transformer having a primary coil and a secondary coil, a circuit for the discharge of said capacitor through said primary coil, said circuit including a triggered gate element having a trigger terminal, said triggered gate element being one which is normally non-conducting so as to prevent the discharge of said capacitor through said primary coil and which is triggered to a conducting state by a trigger signal applied to its trigger terminal to permit the discharge of said capacitor through said primary coil, a permanent magnet means adapted for rotation in synchronism with the operation of the engine with which said system is used, a first core of magnetic material located adjacent the path of said magnet means and having a first pole through which a pulse of flux from said magnet means passes each time said magnet means is moved past said pole in the course of its rotation, and a trigger coil mounted on said pole and connected with said trigger terminal of said triggered gate element for triggering said triggered gate element to its conducting state by the voltage induced in said trigger coil by said flux pulse, said primary coil and secondary coil also both being mounted on said pole along with said trigger coil.