Aircraft piston engine magneto and ignition systems

Abstract

The aircraft piston engine magneto has a magnetic rotor and an ignition circuit with a reconfigurable charge coil inductively coupled to the magnetic rotor. The charge coil is inductively powered by the magnetic rotor and includes multiple coils that are electronically reconfigurable from a high-turn, low-current power coil for use during low-speed operation to a low-turn, high-current power coil for high-speed operation. The charge coil is configured to a high-turn coil by electronically connecting multiple coils in series or a low-turn power coil by electronically connecting coils in parallel. The ignition circuit is a fully electronically controlled ignition circuit that uses only non-mechanically operated electrical components within the magneto to generate and distribute ignition pulses to the piston engine spark plugs.

Description

[Technical Field]

[0001] The present invention relates to a magneto ignition system for an aircraft piston engine. background A typical magneto for an aircraft piston engine ignition system contains all of the mechanical and electrical components necessary to generate and time the ignition pulse that is delivered to the spark plug via the ignition lead. A key advantage of magneto-driven ignition systems is that once the engine is started, the magneto can operate without the need for a battery or other external power source.

[0002] As shown diagrammatically in Figure 12, most magnetos in use today include a permanent magnet rotor, also known as a magnetic rotor, driven from an external input and rotating synchronously with the engine crankshaft at the same speed; a primary coil used to store energy from the rotor's changing magnetic flux as it rotates; a secondary coil inductively coupled to the primary coil to provide a stepped-up high voltage when current through the primary coil is interrupted; a contact breaker to trigger the interruption of current through the primary coil; a camshaft with a cam that mechanically opens and closes the contact breaker in synchronization with the crankshaft angular position; and a distributor with rotary switch terminals connected to the secondary coil to sequentially distribute ignition pulses to the spark plugs in the different cylinders. Both the camshaft and distributor switch rotate via the rotor, so that the input mechanical rotation that drives the magneto is transmitted via the rotor to the camshaft and distributor switch. This can be seen in Figures 13 and 14 for a typical magneto. A camshaft is formed by the end of the rotor opposite the input end, and the camshaft includes an axially positioned slot into which the cam is press-fit to engage the movable blocking point of the contact breaker. The distributor rotary switch operates through meshing gears including a distributor drive gear assembled on the camshaft above the cam and a driven gear to which the rotary switch in the distributor is attached. Such mechanically functioning magnetos, including at least a cam-driven contact breaker and distributor, are referred to herein as mechanical magnetos.

[0003] To obtain the proper timing of the spark in each cylinder, the rotor pole's angular position must be set relative to the crankshaft cylinder's TDC. The rotor pole's angular position, once set, is maintained via a transmission from the crankshaft, as is the distributor's rotary switch. However, with mechanical magnetos, physical wear of components from in-service use can affect the actual timing of the ignition pulse relative to TDC (top dead center), particularly on the cam and its contact breaker. As a result, this timing is typically checked and, if necessary, recalibrated to TDC every 100 hours of operation, with internal inspections of the magneto and replacement of worn components occurring every 500 hours. These checks and inspections increase the service and maintenance burden on aircraft engines, as they occur at intervals much shorter than the typical 2,000-hour engine overhaul schedule.

[0004] Apart from calibrating the rotor angular position relative to TDC, basic adjustment of the ignition timing is also required. Unlike more complex internal combustion engines used in the automotive industry, the spark timing of magneto-type aircraft piston engines is generally fixed (not variable) relative to the piston top dead center (TDC). For maximum efficiency at normal flight operating speeds, the fixed timing is set approximately 20° before TDC (BTDC). However, at lower starting speeds, this cycle is too early, resulting in cylinder spark during the compression stroke before TDC is reached. Therefore, for slower engine speeds (e.g., <600 rpm), many magnetos include an impulse coupling connected between the permanent magnet rotor and its input drive. The impulse coupling contains one or more pawls that are designed to stop and release contact with a stop pin as the coupling rotates. This results in one or more rotor pauses during each rotation, while loading a coil spring that releases at the end of each pause to provide a rapid return to rotation of the rotor. In this way, the rotor accelerates after a pause to catch up with the input drive, thereby generating enough magnetic flux in the magneto to fire the spark plug. These pauses in rotation are created by interference contact between one or more pawls on the impulse coupling and at least one stop pin on the magneto housing. At higher speeds, the impulse coupling pawls are displaced from their functional position due to centripetal forces acting against them. This allows the rotor to operate continuously at the same speed as the input drive. This input coupling is yet another mechanical component subject to wear that must be inspected (and replaced, if necessary) multiple times during a typical 2000-hour engine overhaul.

[0005] Retard contact breakers are used on some mechanical magnetos in place of impulse couplings. They have the advantage of reducing the mechanical wear problems of impulse couplings, but only solve the ignition timing problem at slower engine speeds and do nothing to help the magneto generate enough power to execute ignition. Therefore, they require aircraft battery power and a starting vibrator to generate a pulse from battery power supplied to the magneto's primary coil via the pilot's P lead. Because they require an external power input to operate, such retard breaker magnetos are not electrically self-starting and have the same mechanical problems of cams, camshafts, contact breakers (two sets), and distributors as other conventional magnetos.

[0006] overview According to one aspect of the present invention, a magneto for an aircraft piston engine is provided having a magnetic rotor and an ignition circuit including a charge coil inductively coupled to magnetic poles of the rotor, the charge coil including a plurality of power coils electronically reconfigurable by the ignition circuit between series and parallel connections of the power coils. In at least some embodiments, the magneto includes a fully electronically controlled magneto that generates and outputs ignition pulses using an ignition circuit including only non-mechanically operated electrical components. The ignition circuit may include a position sensor disposed adjacent to at least one magnet carried by the rotor, and the ignition circuit derives power and data solely from the rotating magnetic field generated by the rotor during rotation.

[0007] According to another aspect of the present invention, an aircraft piston engine magneto is provided having a magnetic rotor and an ignition circuit including a reconfigurable charge coil inductively coupled to magnetic poles of the rotor, the reconfigurable charge coil including a plurality of coils inductively powered by the magnetic rotor and electronically reconfigurable from a high-turn, low-current power coil for use during low-speed operation to a low-turn, high-current power coil for use during high-speed operation. In at least some embodiments, the charge coil is configured as a high-turn, low-current power coil by electronically connecting the plurality of coils in series, and as a low-turn, high-current power coil by electronically connecting the plurality of coils in parallel. The ignition circuit may include a speed detector that detects whether the magnetic rotor, as it rotates, indicates an engine speed above or below a speed threshold, and the ignition circuit can configure the plurality of coils in series when the speed detector indicates that the engine speed is below the speed threshold, and can configure the charge coils in parallel when the speed detector indicates that the engine speed is above the speed threshold. The ignition circuit may include only non-mechanically operated electrical components, whereby the magneto includes a fully electronically controlled magneto, and the ignition circuit may include a position sensor positioned adjacent to at least one magnet carried by the rotor, whereby the ignition circuit derives power and data solely from the rotating magnetic field generated by the rotor during rotation.

[0008] According to yet another aspect of the present invention, a magneto is provided, comprising: a housing; a rotor assembly mounted within the housing, the rotor assembly including a magnetic rotor and at least one bearing supporting the rotor for rotation within the housing, the rotor assembly having a first end and a second end, the rotor having a permanent magnet assembly disposed between the first end and the second end, the first end being externally accessible through an opening in the housing so that the rotor can be driven in rotation by an external drive component; and an ignition circuit comprising circuit components, each including at least one power coil and a position sensor, inductively coupled to the magnetic rotor, the ignition circuit including high-voltage output terminals mounted in a location accessible from the exterior of the housing. The rotor assembly is a terminal mechanical device such that the rotor rotates within the housing without transmitting its mechanical motion to any of the circuit components. In at least some embodiments, the ignition circuit is a fully electronically controlled ignition circuit that generates and distributes ignition pulses to the output terminals using only non-mechanically operated electrical components within the magneto. The ignition circuit may include multiple power coils that are electronically reconfigurable by the ignition circuit between series and parallel connections of the power coils.

[0009] According to yet another aspect of the present invention, there is provided a piston engine ignition system that is mechanically powered from a single magnetic rotor and has a plurality of high voltage output terminals adapted to connect to ignition leads to supply ignition energy to one or more spark plugs via the ignition leads, the ignition system comprising a fully electronically controlled ignition circuit that operates from power supplied solely via induction from the magnetic rotor, the ignition circuit generating ignition energy from the received power and selectively distributing the ignition energy as high voltage ignition pulses to the output terminals, the ignition circuit comprising a position sensor that detects a rotational angle of the magnetic rotor, and further comprising control logic that controls timing of the ignition pulses relative to the rotational angle of the magnetic rotor as a function of rotor speed based on rotational angle data from the position sensor.

[0010] The magneto may include any of the following features or any technically feasible combination of the following features:

[0011] The control logic further comprises a speed detector that causes a change in the firing timing of the ignition pulse depending on whether the rotor speed is above or below a predetermined speed.

[0012] - The speed detector includes timing and logic circuitry that controls the advance and retard of ignition timing relative to the output of a position sensor that indicates the engine piston is at top dead center (TDC).

[0013] The speed detector sets the ignition timing to a first firing angle when the rotor speed is within a range of approximately 100 rpm to a predetermined speed, and advances the ignition timing to a second firing angle that is earlier than the first firing angle when the rotor speed is above the predetermined speed.

[0014] The first firing angle is approximately 0-10° after TDC, the second firing angle is approximately 18-28° before TDC, and the predetermined speed is in the range of 250-600 rpm.

[0015] The position sensor is a magnetoresistive sensor that outputs rotation angle data as quadrature sinusoidal waveforms indicative of the rotation angle of the magnetic rotor, and the control circuit includes logic circuitry that uses the sinusoidal waveforms to enable firing of ignition pulses only during specific rotation angles of the rotor.

[0016] the ignition circuit includes a plurality of power coils positioned adjacent to the magnetic rotor at a first angular position such that the power coils provide power to operate the ignition circuit, and the position sensor positioned adjacent to the magnetic rotor at a second angular position such that the position sensor senses magnetic field lines of the magnetic rotor as the rotor rotates.

[0017] The charging coil includes a plurality of power coils that are electronically reconfigurable by the ignition circuit between a series connection and a parallel connection of the power coils.

[0018] According to another aspect of the present invention, there is provided a magneto comprising: a permanent magnet rotor; a ferromagnetic core positioned relative to the rotor to concentrate and induce changing magnetic field lines extending between opposing magnetic poles of the rotor as the rotor spins; and an ignition circuit that inductively extracts power from the changing magnetic field lines, the ignition circuit including: a power circuit having a reconfigurable charge coil wound around the core and comprising a plurality of power coils that supply inductive power to one or more output nodes of the power circuit; a high voltage discharge circuit connected to the output nodes of the power circuit and generating high voltage spark energy at a plurality of high voltage output terminals; and a control circuit connected to at least one of the output nodes of the power circuit and operable under power from at least one of the output nodes of the power circuit, the control circuit including a control output connected to both the power circuit and the discharge circuit, at least one control output to the power circuit that electronically configures the power coils in either series or parallel, and at least another control output connected to the discharge circuit that causes a high voltage ignition pulse suitable for firing a spark plug.

[0019] According to yet another aspect of the present invention, there is provided a magneto comprising a permanent magnet rotor, a ferromagnetic core positioned relative to the rotor to concentrate and induce changing magnetic field lines extending between opposing magnetic poles of the rotor as the rotor spins, and an ignition circuit for inductively extracting power from the changing magnetic field lines, the ignition circuit comprising: a power circuit having a plurality of power coils wound around a core and supplying inductive power to one or more output nodes of the power circuit; a capacitive discharge ignition (CDI) discharge circuit having at least one ignition storage capacitor charged via one or more output nodes, at least one ignition coil configured as a step-up transformer having a primary coil and an inductively coupled secondary coil connected to one or more outputs of the CDI discharge circuit, and at least one controllable solid-state switch, the solid-state switch and primary coil connected in series in circuit across the ignition storage capacitor such that upon activation of the solid-state switch, charge from the ignition storage capacitor flows through the switch and primary coil, thereby establishing a magnetic field that remains until the solid-state switch is deactivated, at which point current through the primary coil is interrupted and a high voltage pulse is induced across the secondary coil; a control circuit including at least one operating power storage capacitor, a position sensor disposed adjacent to the magnetic rotor to detect magnetic field lines emanating from the rotor as it rotates, and a timing circuit to control operation of the solid-state switch based on the rotor angular position sensed by the position sensor; Including, The control circuit's operating power storage capacitor is connected to the ignition storage capacitor through a diode that allows charging of the operating power storage capacitor and prevents it from discharging due to reverse current flow to the ignition storage capacitor, so that the power coil supplies operating power to both the ignition circuit and the control circuit.

[0020] In at least some embodiments, the control circuit includes at least two dc voltage regulators connected to receive input power from the operating power storage capacitor and output two different dc voltages for operation of the logic circuitry. The multiple power coils may be electronically reconfigurable by the ignition circuitry between a series connection and a parallel connection of the power coils.

[0021] BRIEF DESCRIPTION OF THE DRAWINGS Preferred exemplary embodiments of the present invention are described below in conjunction with the accompanying drawings, in which like designations refer to like elements, and in which: [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a perspective view of a portion of a four-cylinder aircraft piston engine having a left magneto constructed in accordance with an embodiment of the present invention and shown in a partially exploded view; FIG. [Figure 2] FIG. 2 is an exploded view of the rotor assembly used in the left magneto of FIG. 1. [Figure 3] FIG. [Figure 4] FIG. 1 is a partial perspective view of a portion of a rotor assembly that connects to a housing and a piston engine. [Figure 5A] FIG. 1 is a diagram schematically depicting one embodiment of a rotor assembly, position sensor, and power coil used to implement a fully electronically controlled magneto. [Figure 5B] FIG. 10 is a diagram schematically depicting another embodiment of a rotor assembly, position sensor, and power coil used to implement a fully electronically controlled magneto. [Figure 6] FIG. 1 is a block diagram of an ignition circuit for a fully electronically controlled magneto configured in accordance with an embodiment of the present invention to be electronically connected to the four spark plugs of a four-cylinder aircraft piston engine. [Figure 7] FIG. 7 is a schematic diagram of a tank capacitor circuit of the ignition circuit of FIG. [Figure 8] FIG. 7 is a schematic diagram of the power circuit of the ignition circuit of FIG. [Figure 8A] FIG. 9 shows a portion of the power circuit of FIG. 8 including a slow start circuit. [Figure 8B] FIG. 9 shows a portion of the power circuit of FIG. 8 including a normal mode circuit. [Figure 8C] 9 shows a portion of the power circuit of FIG. 8 including a shutdown circuit. [Figure 8D] 9 shows a portion of the power circuit of FIG. 8 including an overvoltage protection circuit. [Figure 9] 7A and 7B are electrical schematic diagrams which together depict the control circuit of FIG. 6. [Figure 10] 7A and 7B are electrical schematic diagrams which together depict the control circuit of FIG. 6. [Figure 11] 1 is a graph showing quadrature sine wave outputs of position sensors during magneto operation and depicting various regions and set points used to implement ignition timing with a fully electronically controlled magneto. [Figure 12] FIG. 1 depicts a prior art mechanical magneto using a contact breaker and rotary switch distributor to power the spark plugs of a piston aircraft engine. [Figure 13] FIG. 1 depicts a prior art mechanical magneto using a contact breaker and rotary switch distributor to power the spark plugs of a piston aircraft engine. [Figure 14] FIG. 1 depicts a prior art mechanical magneto using a contact breaker and rotary switch distributor to power the spark plugs of a piston aircraft engine. DETAILED DESCRIPTION OF THE INVENTION

[0023] Detailed Description 1 shows a portion of a four-cylinder aircraft piston engine 20, including an engine auxiliary housing 22 mounted with a pair of fully electronically controlled magnetos 24, 26 configured in accordance with one embodiment of the present invention. The two magnetos may be identical and are provided for redundancy, with the left magneto 24 driving the upper spark plugs of each of the four cylinders and the right magneto 26 driving the lower spark plugs of each of those same cylinders. In this manner, all cylinders can be operated with one or both of the two magnetos. The structure and operation of the left magneto 24 is described below, although it is understood that the structure and operation of the right magneto 26 may be identical.

[0024] Generally, the magneto 24 shown and described below comprises three major components or subassemblies: a housing 30, a magnetic rotor assembly 50 (FIG. 2), and an ignition circuit 64 (FIG. 6). Unlike a mechanical magneto, the rotor 52 of the rotor assembly 50 is not used to actuate additional mechanical components in an internal ignition circuit. Instead, an angular position sensor 66 (FIGS. 5A, 5B, 6, and 9) is used in combination with the rotating rotor 52 to determine the rotor angle and electronically generate the desired ignition timing to properly fire the engine spark plugs. As described below, this fully electronically controlled magneto structure is made possible using a reconfigurable charge coil configuration that is inductively powered from the magnetic rotor 52 and includes multiple coils that can be electronically reconfigured from a high-turn, low-current power coil for low-speed operation to a low-turn, high-current power coil for high-speed operation. This allows the magneto 24 to generate sufficient spark voltage even at low speeds without an external power connection and without impulse coupling or other mechanical means to generate ignition energy. In the following description, the magneto housing 30, rotor assembly 50, power extraction, and rotor position sensing are described, followed by the ignition circuit 64.

[0025] The magneto housing 30 holds and provides a sealed enclosure for the rotor assembly 50 and ignition circuit 64. As shown in FIGS. 3 and 4, the housing 30 may be a two-piece housing having a lower frame 31 and an upper cap 32 that can be fastened to the frame 31 along a split line 33. Removable fasteners, such as screws or bolts, or permanent fasteners, such as rivets, can be used for this purpose. The housing 30 has an opening 34 in its lower frame 31 through which the rotor 52 can be connected to the engine 20, and has a woodruff key 35, flats, or other means used to lock the rotation of the rotor 52 to whatever drive components are used to mechanically power it. The housing 30 further includes four high-voltage output terminals 36 mounted in externally accessible positions on the upper cap 32 to which ignition leads can be connected to deliver ignition impulses from the magneto 24 to spark plugs (shown diagrammatically in FIG. 6). The ignition leads and spark plugs may be conventional or other.

[0026] Referring back to FIG. 1 , the components of the mounting interface of the left magneto 24 to the engine 20 are shown in an exploded view, including an adapter 37 and gasket 38 for sealing the opening 34 in the magneto housing to a corresponding opening 39 in the engine auxiliary housing 22. This interface also includes an external drive component 40 in the form of an external gear having an integral hub 41 with a slotted cutout on its axial front face along with a drive slot 42 for transmitting rotational motion to a rotor assembly input coupling 51 ( FIG. 2 ). The external drive gear 40 mates with the input end of the rotor 52; however, it is external in that it is not part of the magneto and is actually located within the engine auxiliary housing 22 during use. The drive gear 40 meshes with an upstream gear in the engine that is driven directly or indirectly from the crankshaft using a gear ratio that results in the external drive gear rotating at the same speed as the crankshaft. Thus, the rotational angle of the external drive gear matches the rotational angle of the crankshaft position. FIG. 2 shows a mechanical input coupling 51 that can be rigidly secured to the rotor 52 for rotation therewith. The input coupling includes a drive lobe 53 fixed to mate with the drive slot 42 of the external drive gear 40 to provide positive driving engagement of the input coupling 51. In this manner, the rotor 52 is directly driven by the external drive gear 40 such that rotation of the rotor is locked to rotation of the engine crankshaft.

[0027] This drive lobe / slot coupling for transmitting drive to the rotor 52 is typical of mechanical magnetos in that it allows for the use of an impulse coupling where the rotor is not locked to the external drive component but is driven through a lobed coupling shell, and further allows a non-impulse coupled magneto to utilize the same slotted external drive component using a simple lobed input coupling locked to the rotor, as shown in FIG. 2. However, for the fully electronically controlled magneto 24 described herein, other simpler drive connections can be used, such as by securing the external drive gear 40 to the rotor 52 in a locked manner that does not allow relative rotation therebetween. This provides a more direct drive of the magneto rotor using fewer parts.

[0028] The rotor 52 comprises part of a rotor assembly 50, which typically includes both an inner bearing 54 and an outer bearing 55, although the rotor 52 also includes at least one bearing. These bearings 54, 55 are used to rotatably mount the rotor 52 within the magneto housing 30. The rotor 52 includes a lobed mechanical input coupling 51 (shown in an opposite perspective from the other components in FIG. 2 ). The rotor 52 extends from a first end 56 to a second end 57 and includes a permanent magnet assembly 58 located between the first end 56 and the second end 57. The permanent magnet assembly 58 can be a conventional or unconventional configuration of one or more magnets 59 presenting one or more pairs of strong magnetic poles facing radially outward. These magnets 59 are referred to herein as power magnets because they are used in combination with a charging coil of an ignition circuit 64 to generate the electrical power required to operate and ignite the spark plug. The rotor 52 further includes a sensor magnet 60 mounted within a radial slot 61 located at the second end of the rotor 52. The angular position sensor 66 itself is mounted on the housing 30 in a position adjacent to and facing this magnet 60 as shown and described in connection with Figures 5A and 5B.

[0029] The rotor assembly 50 does not include an impulse coupling, retard breaker, camshaft, cams, or distributor drive gear. As a result, it is much simpler to design and construct than those used in a mechanical magneto. Also, given that the rotor assembly does not drive any additional components within the magneto 24, it constitutes a “terminal mechanical device,” which, as used herein, means a device that undergoes motion when mechanically driven without transmitting any of its motion to another device. In other words, those skilled in the art will understand that the rotor 52 rotates without any mechanical load, and that the bearings 54, 55 that hold the rotor 52 are not considered mechanical loads. The rotor assembly 50 is the end of a chain of mechanically driven components, which in this case also includes, in drive order, the crankshaft, the internal engine gears to the external drive components within the auxiliary housing 22, and the mechanical input coupling 51 of the rotor assembly 50.

[0030] The elimination of impulse couplings, retard breakers, camshafts, cams, contact breakers, and distributors is achieved through an innovative ignition circuit design that (i) operates solely on power generated within the magneto 24, (ii) includes an electronically reconfigurable charge coil 65 (FIG. 5A et seq.) that generates sufficient magneto power at both low (starting) and full engine speeds, and (iii) is "fully electronically controlled," meaning that the ignition circuit 64 utilizes only non-mechanically operated electrical components within the magneto 24 to generate and distribute ignition pulses. This fully electronically controlled ignition circuit 64 with its reconfigurable charge coil 65 enables an ignition circuit that, once the engine is started from the starter motor or from appropriate manual rotation of the propeller, ignition via the magneto 24 can begin at engine speeds below approximately 100 rpm and can continue throughout the entire range of engine speeds. This fully electronically controlled magneto 24 also takes advantage of the fact that all mechanically operated circuit components within the mechanical magneto are functionally tied to the need to control the timing and distribution of the ignition pulse. In the illustrated embodiment, the ignition timing function is accomplished electronically using a single angular position sensor 66 (FIGS. 5A, 5B, 6, and 9) located adjacent to the sensor magnet 60 of the rotor 52 to detect the instantaneous angular position of the rotor, and therefore the engine crankshaft. As described below, distribution of ignition pulses to the cylinders is accomplished electronically using multiple ignition channels, each with its own ignition coil.

[0031] In general, the position sensor 66 may be any suitable angle sensor, whether fixed, continuously variable, or variable between two or more speed ranges, that outputs rotational angle data with sufficient accuracy and resolution to be used by the ignition circuit 64 to provide speed detection and proper ignition timing. To this end, the sensor 66 should be a sensor that determines rotor angular position with sufficient accuracy and resolution to be used by the ignition circuit 64 in properly timing ignition pulses. In the illustrated embodiment, the position sensor 66 is a magnetoresistive sensor that provides quadrature sinusoidal signals used by the ignition circuit 64 to determine the angular position of the rotor 52 and, therefore, the engine piston position relative to its TDC. An exemplary magnetoresistive sensor that may be used is a commercially available TLE5501TMR-based angle sensor. Depending on the particular magneto application, optical and other non-magnetic angle sensors may be used in some embodiments.

[0032] FIG. 5A diagrammatically illustrates the design of a reconfigurable charging coil 65 used to extract power from the rotating magnetic field generated by the rotor 52, as well as the incorporation of a position sensor 66 into the housing 30 adjacent to the rotor. The charging coil 65 comprises four separate power coils 68 (individually labeled L1A, L1B, L1C, and L1D in the schematic diagrams of FIGS. 8-8D), each constructed of the same wire and number of turns, wound on a ferromagnetic core 69 located within the housing 30 adjacent to the power magnets 59 of the rotor 52 to concentrate and guide the changing magnetic field lines extending between the opposing magnetic poles of the rotor 52 as the rotor spins. The instantaneous rotor position in FIG. 5A illustrates the rotor angle at which maximum magnetic flux occurs in the core 69. The magnetic field lines are generally shown with a north-to-south field line direction indicated by the arrows. As the rotor continues to rotate, the magnetic field decays to zero, then reverses direction, and increases again to maximum flux when the rotor reaches 90° from the illustrated position. These increasing and collapsing magnetic fields induce current through each of the four power coils 68, allowing them to be used in the ignition circuit 64 as four separate power sources that are ganged together to generate sufficient dc voltage and current to ignite the engine spark plugs via the ignition coils.

[0033] Additionally, the four power coils 68 can be electronically configured by the ignition circuit 64 in a series or parallel connection of coils, allowing the magneto 24 to be self-powered over the entire range of engine speeds from start-up to maximum rpm, all without the need for external power connections or extraneous mechanical parts.

[0034] The position sensor may be mounted on a printed circuit board (PCB), as shown in FIG. 5A, where the sensor 66 and PCB are collectively referred to as the sensor board 67. This sensor board 67 is mounted to the housing 30 adjacent to the sensor magnet 60 of the rotor 52, and it is axially spaced from the power magnet 59 to avoid interfering magnetic fields. In FIG. 5A, an end view of the rotor 52 is shown, with the magnet 60 secured within a slot 61 in the second end 57 of the rotor. The sensor board 67 is also shown to illustrate its positioning relative to the sensor magnet 60, and although not shown in this view, it is secured to the magneto housing 30 in this position and orientation. In contrast to the four-pole power magnet 59, the sensor magnet 60 includes a single north-south pole pair so that the sensor 66 generates one complete pair of orthogonal sinusoidal waveforms for each rotation of the rotor 52.

[0035] The fixed rotational direction of the sensor magnet 60 on the rotor is shown at an angle α relative to the rotational direction of the power magnet 59. Specifically, this angle α is the angle measured between the centerline of the north and south pole of the sensor magnet 60 and a particular pole of the power magnet 59. While the illustrated angle α is arbitrary, in use, this angle is advantageously predetermined so that the magneto is synchronized to the piston TDC. For example, the north pole of the sensor magnet can be oriented directly adjacent to the position sensor (e.g., at the 3 o'clock position shown in FIG. 5A), thereby placing the poles of the power magnet in a desired alignment with the ferromagnetic core and coil. This desired alignment could be, for example, a position that provides maximum or minimum magnetic flux to the core 69, or something therebetween, providing advantageous or optimal timing of coil energization relative to ignition pulse timing. Such alignment can be determined during the design phase and / or through testing.

[0036] FIG. 5B depicts an alternative sensor arrangement, in which the sensor substrate 67 is positioned adjacent to the permanent magnet assembly 58 of the rotor 52 at an angular (or circumferential) position offset from the positions of the power coil 68 and ferromagnetic core 69. This offset position forms an angle β from the angular position of the coil 68 and core 69. This angle is shown as being large enough to avoid interference by the coil and core with the magnetic field sensed by the sensor 66. It can be selected within a range of 90 to 180 degrees to the right or left of the vertical centerline shown in FIG. 5B, and angles less than 90 degrees may be used depending on the circumferential extent of the coil / core package. In this embodiment, the rotor 52 does not need to have a separate sensor magnet 60 because the same magnet 59 used to energize the power coil 68 is also used for rotor position sensing. However, this component count reduction benefit may be offset by greater difficulty in obtaining adequate position accuracy and resolution and resulting more complex processing circuitry.

[0037] In this embodiment, it is also advantageous to synchronize the position sensor output signal with piston TDC to provide the desired angular alignment of power magnet 59 with power coil 68. This can be done by determining and fixing the position of sensor substrate 67 within housing 30 relative to the angular position of the rotor poles so that the desired alignment with coil 68 is achieved. Such position may be at or between any of the discrete optional positions shown in FIG. 5B as determined by design and / or testing.

[0038] 6-10, the ignition circuit 64 will be described. FIG. 6 is a functional block diagram of the ignition circuit 64 of the fully electronically controlled magneto 24, shown connected to four spark plugs 70 by ignition leads 71. The ignition circuit 64 includes a position sensor 66 and a reconfigurable charge coil 65, from which the ignition circuit 64 obtains its only magnetic field input, and only from the rotating magnetic rotor 52. One magnetic input is the reversing magnetic field from the power magnet 59, and the other magnetic input is from the position sensor magnet 60. The ignition circuit 64 is logically and (for the most part) physically separated into three main circuits: a power circuit 80, a control circuit 90, and a discharge circuit 100. The power circuit 80 and the control circuit 90 are implemented on separate printed circuit boards (PCBs) mounted within the housing 30, while the discharge circuit 100 is a largely separately packaged component also mounted within the housing. The circuit board and the individual discharge circuit components are interconnected by soldered wires extending therebetween.

[0039] Generally, power is extracted by a charging coil 65 consisting of four power coils 68 (L1A-L1D). This extracted power is induced in the power coils 68 from the changing magnetic field lines generated by the rotor 52 during rotation. These coils 68 form part of a power circuit 80, which is positioned adjacent to the rotor 52 for inductive coupling. The power circuit 80 uses the induced current from the coils 68 to charge a tank (or storage) capacitor in a tank capacitor circuit 74. This stored charge from the tank capacitor circuit 74 provides the power required to operate the control circuits as well as the energy required by the discharge circuit to fire the spark plug 70. For a four-stroke, four-cylinder engine with two pairs of identically timed (i.e., having the same TDC) pistons reciprocating together at 180° or some other angle relative to the other pair, the ignition circuit 64 can be configured to operate in a wasted spark configuration in which cylinders 1 and 4 fire together (and cylinders 2 and 3 fire together), even if one of the cylinders in each pair is near TDC between the exhaust and intake strokes rather than between the compression and power strokes. This allows the ignition system to operate with only two channels, A and B, using only two ignition coils 72 with different ends of their secondary coils connected to different spark plugs 70 in different ones of the two cylinders in the pair.

[0040] Although various spark generation circuits may be used, the illustrated embodiment uses a capacitive discharge ignition (CDI) scheme in which charge stored in tank capacitor circuit 74 is drawn through the primary coil of ignition coil 72 by power transistors QA and QB (FIG. 10) and then abruptly interrupted by turning the transistors off, thereby creating a large voltage across the secondary coil of each ignition coil, as is known, which is described further below in connection with the structure and operation of discharge circuit 100.

[0041] Sufficient power for the ignition circuit 64 and plug spark can be achieved at both starting and normal speeds without a separate power source by using multiple power coils 68 wound on a core 69, with the coil outputs, whether adjacent or overlapping, summed together to generate sufficient voltage and current to charge a tank capacitor circuit 74 to the voltage required to fire the spark plug 70 via an ignition coil 72. In the illustrated embodiment, four power coils 68 are used to generate this charging current using a reconfigurable charging coil approach that sums or overlaps the coil voltages at slow speeds and sums the coil currents at fast speeds. While four coils are used in the illustrated embodiment, other embodiments may use more or fewer power coils as desired or required for a particular application.

[0042] As shown in FIG. 7, four capacitors are used that together form a hardwired tank capacitor circuit 74. Each capacitor TC1-TC4 can be identical, such as 47 uF, although different capacitances may also be used. As will be apparent from inspection of the power circuit in FIG. 8, capacitors TC1 and TC2 are wired in combination with the diode-steered sum voltage from the power coil 68 to act as a voltage doubler to help charge tank capacitor TC3 to a sufficient dc voltage. Also, as shown in FIG. 6, tank capacitor circuit 74, and in particular tank capacitor TC3, provides operating power to control circuit 90. To decouple the discharge of TC3 during an ignition event from control circuit operation, this power supply from TC3 is used to charge a fourth capacitor TC4 through diode 75 mounted on the control circuit board, which prevents reverse power draw from TC4. Thus, both TC3 and TC4 act as storage capacitors or tank capacitors to provide power to operate the ignition coil and the control circuit, respectively.

[0043] FIG. 8 depicts power circuit 80. It is a mostly analog circuit including four power coils 680 and four associated subcircuits: low-speed (start) circuit 82, normal-mode circuit 84, shutdown circuit 86, and overvoltage protection circuit 88. Shutdown circuit 86 is connected to the standard pilot's P lead, which prevents magneto operation when shorted and allows magneto energization, and therefore engine operation, when open. Opening the P lead connection allows an engine starter motor or other means to be used to rotate the engine and initiate magneto operating power generation and cylinder ignition. To this end, ignition circuit 64 begins in start mode using low-speed circuit 82, configured to generate sufficient magneto operating power and spark energy to fire spark plug 70 even at low engine speeds of 100 rpm or sometimes less, depending on the details of circuit design and component selection. Once the engine begins operating on its own, it speeds up to above a threshold engine speed, typically about 600 rpm. Power circuit 80 then switches to its normal operating mode using normal mode circuit 84 to generate the appropriate charging voltage and current for tank capacitor TC3.

[0044] Engine shutdown can be manually controlled by the P lead via a pilot ignition switch (not shown), which grounds the P lead. This switches power circuit 80 into shutdown mode by activating shutdown circuit 86, which shorts out one or more of the power coils 68, thereby preventing any of the four inductively coupled power coils 68 from providing operating power. In the absence of ignition spark, the engine will rev slowly to a stop.

[0045] The overvoltage protection circuit 88 utilizes some of the same circuitry used for shutdown to shunt one or more power coils 68 intermittently (i.e., on each charging cycle as needed) when the voltage on tank capacitor TC3 reaches its maximum desired charging voltage, as well as following an ignition impulse, to ensure that the voltage on TC3 does not rise too quickly.

[0046] All power circuit components can be integrated together on a PCB, except for the power coils 68 (i.e., L1A, L1B, L1C, and L1D) wrapped around a ferromagnetic core 69 adjacent to the magnetic rotor 52. The eight leads from these coils 68 can be soldered to the PCB at their designated electrical pads. As will be appreciated, the only power input to the power circuit 80 is the magnetic field lines from the rotating rotor's power magnets 59. Power coils L1A-L1D are all wound with the same polarity on the core 69, as shown. High-voltage, low-current power coils, such as those formed by 1,000 or more windings per coil, can be combined to provide sufficient power by combining the voltages in series for low-speed operation or the currents in parallel for high-speed (normal) engine operation. In this way, a single charge coil package can fit within a standard magneto housing and be electronically reconfigured into different coil configurations for different power and ignition needs. This reconfiguration of the charging coil also enables magneto 24 to generate enough voltage across reservoir capacitor TC3 to fire a typical aircraft piston engine spark plug 70 once per crankshaft revolution at speeds below 100 rpm without a mechanical impulse coupling or external power source.

[0047] The power circuit 80 has five control inputs, the first of which is the pilot ignition switch P lead, part of the shutdown circuit 86, which, when grounded, cuts off engine ignition power. This means it is in an open (high impedance) state to allow operation of the ignition circuit. The other four control inputs to the power circuit 80 come from the control circuit 90. Two of these, identified by off-board wire connections labeled purple and white, are for controlling the power circuit mode between starting and normal operating modes. The other two, identified by wire connections labeled yellow and blue, cut off the power coil charging of the tank capacitor during the ignition impulse, as explained below.

[0048] Power circuit 80 has three power outputs that connect to tank capacitor circuit 74 (see FIG. 7), which is part of discharge circuit 100, and includes four individual capacitors TC1-TC4. These capacitors are potted and off-board, and are connected by wiring using the color coding shown. As will be understood by those skilled in the art, the D11 / D13 / D25 / D26 diode steering connections to capacitors TC1 and TC2 form a modified voltage multiplier for the power supplied by the four L1 power coils 68.

[0049] 8A-8D depict different portions of the power circuit 80 of FIG. 8, with the four portions shown including four different sub-circuits 82, 84, 86, 88 of the power circuit 80. For each of FIGS. 8A-8D, only the particular sub-circuit is shown, with the remainder of the power circuit 80 being grayed out to aid in identifying the sub-circuit components being described.

[0050] FIG. 8A depicts a slow-speed starting circuit 82 used to generate magneto and spark power at very low engine rpm. This circuit 82 is activated by a control circuit 90 using a transistor switch Q2A (FIG. 10) that switches the power circuit's operating mode between starting and normal based on engine speed. A speed detector 93 (FIG. 10) operating off of the position sensor 66 is used to determine this rotor / engine speed. When in starting mode, switch Q2A is placed in the off (non-conducting) state, preventing current flow through the U3-U8 opto-isolators, keeping them off, and also keeping thyristors (SCRs) Q13, Q15, Q17, Q20, Q21, and Q24 off. As a result, a forward bias voltage energizes the gates of thyristors Q12, Q14, Q18, Q19, Q22, and Q23, which electrically connect power inductors L1A-L1D together in series and with diodes D11, D13, D25, and D26 into a full-wave rectifier, which also forms a modified voltage multiplier in combination with capacitors TC1-TC3.

[0051] In this starting mode, the voltage stack of four power coils 68 electronically connected in series helps overcome the lower induced voltages that occur at the slower rotational speeds of the magnetic rotor 52. This starting circuit 82 therefore offers an advantage over retard breaker magnetos in that it does not require an external power source or the need to generate a shower of sparks at each engine start. This circuit 82 is also advantageous over impulse-coupled magnetos because it eliminates one of the mechanical wear and possible failure components of those mechanical magnetos.

[0052] Referring now to FIG. 8B, normal mode circuit 84 is shown, which takes over operation of power circuit 80 when the engine is throttled beyond its slow-start range. Control circuit 90 monitors engine speed via angular position sensor 66 by comparing it to a predetermined speed threshold of 600 rpm, although other predetermined speeds above or below 600 rpm may be used. Below this threshold, control circuit 90 maintains power circuit 80 in slow-start mode. Once the threshold is reached or exceeded, control circuit 90 switches power circuit 80 to normal operating mode, in which the circuit of FIG. 8B becomes active. This is accomplished by energizing opto-isolators U3-U8 connected to the gates of thyristors Q13, Q15, Q17, Q20, Q21, and Q24, which allow them to conduct. This electronically reconfigures the four power coils L1A-L1D into parallel-connected coils, which have the effect of forming a low-turn, high-current coil by summing their currents rather than their voltages. Similar to the starting mode, this aggregated power is used to charge tank capacitors TC3 and TC4 through the full-voltage rectifier formed by diodes D11, D13, D25, and D26.

[0053] Due to the high rotational speed of the magnetic rotor 52 during normal engine operation, the corresponding faster rate of reversal of the magnetic field lines acting on the power coils 68 results in a higher voltage per coil than at slower speeds, thus allowing a single power coil 68 to generate a peak voltage sufficient to charge the tank capacitor TC3 to the appropriate voltage. Also, the remaining three power coils 68 connected in parallel with the first coil 68 double the amount of current supplied to charge TC3, allowing the charging coil 65 to reach the appropriate voltage much more quickly than when in a voltage accumulation configuration.

[0054] FIG. 8C depicts the shutdown subcircuit 86, which is activated from the P lead. When the P lead is grounded via the pilot's ignition switch, capacitor C9 discharges through R16 and R17 until transistor Q5A turns off, allowing current to conduct through diodes D3-D5 and resistor R14, forming a voltage divider with R8 that turns on transistor Q3B and grounds the common node between resistors R5 and R6, thereby allowing pnp transistors Q1 and Q2 to conduct. This energizes the gates of thyristors Q11 and Q25, allowing conduction through power coils L1A and L1D, whichever currently has positive polarity in the forward conduction direction of its associated thyristor. Because all four power coils 68 are tightly inductively coupled, the voltage across all coils drops to near zero regardless of rotor rotation. Ignition is then terminated, resulting in the engine being powered down.

[0055] FIG. 8D depicts the fourth subcircuit portion of the power circuit 80, the overvoltage protection circuit 88. This circuit 88 uses the same thyristors Q11 and Q25 to activate when necessary to at least momentarily stop charging the tank capacitors TC3 and TC4 during certain conditions. The first condition is an overvoltage on the tank capacitors. Zener diode Z2, which may be, for example, a 47V, 1 / 2-watt Zener, sets the overvoltage setpoint and, when its breakdown voltage is exceeded, turns on transistor Q3A, whose collector is connected to the same common R5 / R6 node as Q3B, thereby turning on Q1 and Q2 and shunting power coils L1A and L1D in one direction. The second condition that triggers the overvoltage protection circuit is firing of the ignition in each of channels A and B of the two discharge circuits 100 (FIGS. 6 and 10). The same pulse signal used to switch the ignition coil power transistors QA and QB on and off is also used to activate opto-isolators U1 (Channel A) and U2 (Channel B). The opto-isolators therefore operate alternately, each switched on only for the duration of that channel's ignition pulse. When the opto-isolators are activated, current is conducted through a suitable (e.g., 47V or less) Zener diode Z1 and fed to the base of transistor Q3A, temporarily shunting the power coil 68 during ignition. This helps ensure that the voltage on tank capacitor TC3 does not rise too quickly after the spark.

[0056] 9 and 10, there is shown a control circuit 90. As discussed above and shown in FIG. 10, charging power supplied to tank capacitor TC3 is input to the red wire input and charges tank capacitor TC4 through diode D3, which prevents current draw from TC4 by discharge circuit 100 when powering ignition coil 72 for spark ignition. That TC4 operating power runs control circuit 90 and is developed into two regulated voltage supplies, +5v and +12v, using suitable linear, switch mode, or other voltage regulators 91 and 92.

[0057] FIG. 9 depicts the angular position sensor 66, various generated voltage setpoints, an operational amplifier, and a comparator used in conjunction with the setpoints to provide logic-level binary values ​​used by the separate logic circuitry of FIG. 10 to determine the timing of the ignition pulse for each of the two channels. The operational amplifier is located above the horizontal 2SPAN signal line shown in FIG. 9, and the comparator is located below that signal line. The setpoints are indicated by their names and are generated from different fixed and variable voltages, specifically, a +5V logic supply voltage, a tank capacitor TC3, and sine and cosine waveforms provided by the angular position sensor 66 as the rotor 52 rotates. To normalize the setpoints to the sensor peak output, a voltage approximately twice the sensor peak amplitude (2SPAN) is generated and used to determine the various setpoint voltages. Additionally, a minimum expected sensor peak amplitude is determined, for which a separate binary state signal, VSPAN>95%, is generated and used to gate the ignition pulse firing within the timing logic. The position sensor setpoints represent specific points during a single cycle of the sensor output, which occurs once per rotor (and engine) revolution. These points are used by a discrete logic circuit to determine the crankshaft angle and, consequently, the proper ignition timing.

[0058] The selection and use of these position sensor setpoints can be best understood by referring to Figure 11, which shows the quadrature sinusoidal output of the position sensor, both sine and cosine waveforms, generated as the sensor magnet's poles pass the sensor. Ignition timing that mimics the ignition timing of a typical mechanical magneto, such as the Champion Aerospace® Slick® 4371™ magneto, requires a first fixed firing angle for speeds below 600 rpm and a second fixed firing angle for speeds above that predetermined threshold. The first low-speed firing angle is delayed from normal operation at 0° TDC but can be in the range of approximately 0 to 10° after TDC. The second normal-operation firing angle is advanced to 20° before TDC but can be in the range of approximately 18 to 28° before TDC. The 600 rpm setpoint is only an exemplary speed threshold for ignition timing changes. In general, any engine speed within the range of 250 to 600 rpm can be used. Regardless of the setpoints and thresholds selected, separate logic circuits are required to identify the appropriate locations along the course of the periods of these sinusoidal waveforms for firing at different engine speed ranges.

[0059] In the sensor output of Figure 11, each X-axis unit is 15° of rotation, and the sine and cosine amplitudes are normalized to 1.0. The sine wave is used for timing adjustment, and the cosine waveform is used for directionality check. As shown in Figure 11, there are three main regions of interest. The first, Region 1, is any point in the rotation when the sine wave is >0.3 (or 30%) of its peak amplitude. This represents the angular region where the spark is too late for the power stroke, so a setpoint representing this region is used to disable ignition firing during these angles. The second, Region 2, is any time when the cosine wave is <-0.5 (the lower 50%) of its peak amplitude. This is the angular region during which ignition could cause the engine to rotate backwards, so this setpoint is also used to disable ignition firing within this angular region. Region 3 is the angle leading up to the desired spark ignition timing and is used to allow the ignition circuit to generate a timely spark. As noted in FIG. 11, this region occurs when the cosine is >0.5 and the sine is <-0.3.

[0060] Referring back to Figure 9, we can see that these regions are identified by various setpoints developed from the position sensor output, and comparators are used to represent the setpoints and their inverses as binary voltages of 0 / 5v. Thus, 0v represents LO or a binary 0 value, and 5v represents HI or a binary 1 value.

[0061] 10 includes the remainder of the control circuit 90, specifically the control logic that controls the timing of the ignition pulse relative to the magnetic rotor's angle of rotation as a function of rotor speed based on angle of rotation data from the position sensor. This control logic includes a speed detector (circuit) 93 that switches the power circuit 80 between a low-speed mode and a normal-speed mode, thereby varying the timing of the ignition pulse depending on whether the rotor speed is above or below a predetermined speed. The control logic also includes two ignition channels A and B, each with ignition coil firing circuits 94A and 94B, each controlled by both ignition enable circuits 95A and 95B and timing logic 96A and 96B, respectively. The configuration and operation of only the upper ignition channel A (circuits 94A, 95A, 96A) is described, although it will be understood that channel B may be identical.

[0062] The firing enable circuit 95A and timing logic 96A implement the conditions described above and illustrated in FIG. 11. The firing enable circuit 95A uses discrete logic circuits to enforce the requirements of Regions 1-3 based on various state conditions identified by the signals on the left side of the diagram generated by the setpoint and comparator circuits in FIG. 9. Circuit 95A includes an SR latch 95A1. Because commercially available SR latches are set-dominant, the logic used in the circuit is Set (HI) when firing should be disabled / blocked. The upper AND gate 95A2 represents desired Region 3, where ignition firing initiation is desired, and its output is connected to the Reset of the SR latch 95A1. Region 3 is not the angle range in which firing occurs, but rather the region in which firing circuit 94A is switched to an enabled state for subsequent firing. The remaining AND gate 95A3 and three OR gates 95A4, 95A5, 95A6 disable firing by setting SR latch 95A1 HI when in regions 1 or 2, thereby requiring the crankshaft angle to re-enter region 3 on each cycle before firing circuit 94A is re-enabled.

[0063] SR latch 95A1 feeds another SR latch 96A1 in the timing logic connected to its Set input. As a result, when ignition is enabled by the ignition enable circuit 95A, the Set input of timing logic SR latch 96A1 is at logic 0 (LO), allowing its Q output to switch from HI to LO upon reset, which in turn triggers the ignition coil firing circuit 94A. Using three AND gates 96A2, 96A3, and 96A4 and an OR gate 96A5, timing logic 96A sets its SR latch 96A1 reset input if the following conditions are met: 1) tank capacitor TC3 > 45 volts, AND 2) position sensor peak detector (VSPAN) > 95% of minimum expected voltage, AND 3) position sensor is at least at the -10° advance timing point (SIN > NEG_SET), AND 4A) speed > 600 RPM, OR 4B) position sensor 66 is at or beyond the +10° retard firing point (SIN > POS_SET). A binary speed indicator (above or below 600 rpm) is provided by speed detector 93, described below.

[0064] Assuming that the firing enable circuit 95A enables the timing logic 96A to initiate an ignition pulse and the four timing logic conditions described above are met, including reaching either the advance or delay setpoint, the Reset input of the timing logic's SR latch 96A1 switches to HI, thereby setting Q=LO which switches the output of the timing logic from HI to LO.

[0065] The ignition coil firing circuit 94A uses an industry-standard 555 timer to generate a positive firing pulse with a duration set by the R30 / C9 time constant. The 555 timer is triggered by a negative edge at its trigger input, the aforementioned high-to-low transition received from the timing logic's SR latch 96A1, and the resulting output of the 555 timer goes high until the threshold input rises to 0.67*5V (3.35V). The firing circuit 94A also includes a Darlington, push-pull, or other suitable high-gain driver to switch on the power transistor QA for the duration of the 555 timer's output pulse. This pulse width may be set, for example, depending on the magnetic properties of the power coil 68 so that it is saturated by the time the pulse ends and current is shut off.

[0066] The output of the 555 timer also sends a signal back to the firing enable circuit 95A to reset the output of the SR latch to HI so that the trigger input of the 555 timer does not remain LO. The 555 timer also energizes the U1 and U2 opto-isolators of the power circuit 80 to prevent excessive dv / dt after firing.

[0067] The speed detector 93 also uses a 555 timer, as well as a D-type flip-flop (DFF) and a transistor switch Q2A circuit to operate the normal-mode opto-isolators U3-U8 of the power circuit 80. The speed detector 93 includes a timer and logic circuit to control the advance and retard of ignition timing relative to the output of the position sensor 66, which indicates the engine piston is at top dead center (TDC). The speed detector's 555 timer is connected in a one-shot configuration per its datasheet. The speed detector 93 receives a SIN>+0.3 input signal, derived from the angular position sensor 66. To understand how the speed detector 93 functions, assume its timer starts in a wait state (OUT and DISCH are low, and RES and TRIG are high) and the speed detector output is low (indicating less than 600 rpm). The one-shot timer is set for 50 ms (half a revolution at 600 rpm), so the output remains high for at least half a revolution at 600 rpm.

[0068] The output of the speed detector timer is wired to the input of a D-flip-flop (DFF). The output of the DFF is a speed range or state, used to indicate the operating mode (starting or normal) of the power circuit 80. The timer starts when SINE falls below +0.3, and the DFF clock goes HI when the SINE input falls below -0.3 half a revolution later.

[0069] The speed detector timer is triggered when the SINE output of the position sensor 66 exceeds +0.3° (17.5°), as indicated by the SIN>+0.3 signal. The timer is reset (output goes LO) after 50 ms. The clock for the DFF transitions HI when SINE exceeds -0.3° (197.5°), which is one-half revolution after the timer starts, as indicated by the SIN<-0.3 signal. If a half revolution is completed before the timer is reset, this indicates that the engine speed is above 600 rpm, and the speed detector state is set HI, placing the power circuit 80 in high-speed mode, resulting in the spark being triggered at the leading setpoint. Otherwise, the speed detector output remains LO, keeping the power circuit 80 in low-speed mode, resulting in the spark being triggered at the lagging setpoint.

[0070] As will be appreciated, the 600 rpm switch point between low and normal mode operation is only one of many predetermined speeds that can be used. Also, the timing can be adjusted differently, not just between the two firing angles described above. Different firing angles and engine speed ranges can be used; for example, in some embodiments, at starting speeds below a predetermined speed in the range of 250-600 rpm, a first firing angle of approximately 0-10 degrees after TDC is used, above which the predetermined speed becomes a normal engine operating speed at which a second firing angle of approximately 18-28 degrees before TDC is used.

[0071] In still other embodiments, ignition timing can be adjusted more finely, providing anywhere from continuously variable timing to a finer (>2) band of engine speed than the two ranges typically provided by a mechanical magneto. Additional sensor inputs allow timing to be adjusted based not only on engine speed, but also on other factors affecting combustion, such as engine load, engine temperature, throttle position, atmospheric conditions (pressure, temperature, altitude, and / or humidity), air / fuel mixture, and combustion chamber size and / or design.

[0072] When installing the magneto on the engine, the fully electronically controlled magneto 24 must be synchronized with the angular position of the crankshaft. This can be done with a timing light using marks on the flywheel to which the propeller is attached. Coarse magneto synchronization can be achieved by rotating the external drive gear 40 to the correct position on the rotor before meshing it with the engine's internal gear during installation, and then fine-tuning the correct synchronization can be achieved by making small rotational adjustments to the magneto housing 30 before tightening it.

[0073] As described above in connection with FIG. 6 , discharge circuit 100 is a two-channel CDI circuit including a TC3 tank (storage) capacitor charged via the red, gray, and black outputs from power circuit 80, and includes channel A and B ignition coils 72 configured as step-up transformers with their primary coils connected to the high-voltage terminals 36 of magneto 24 and inductively coupled secondary coils connected to ignition leads 71 ​​that deliver ignition pulses to spark plugs 70. Discharge circuit 100 further includes two channels of solid-state transistor switches QA, QB, with the transistor and ignition coil primary of each channel connected in series in circuit across tank capacitor TC3, so that upon transistor activation, charge from TC3 flows through the transistor and primary coil, thereby establishing a magnetic field that remains until the transistor is deactivated, at which point current through the primary coil is interrupted, inducing a high-voltage pulse across the secondary coil that is supplied via ignition lead 71 to the associated spark plug 70.

[0074] The ignition system described above may be adapted for non-aviation applications, such as small engines used in residential and commercial appliances that include at least one spark plug. For such purposes, the rotor 52 and power coil 68 may be modified to have more or fewer poles and coils, and appropriate modifications may be made to the power circuit 80 and control circuit 90 to adjust the timing and number of high voltage outputs for the intended application. Such modifications will be apparent to those skilled in the art.

[0075] Of course, the names of the various circuits, such as power circuit 80 and control circuit 90, are logical constructs to aid in understanding the various functional components of the overall ignition circuit 64, but it will be understood that these functional portions of the ignition circuit 64 may be physically separated within the magneto 24 or may be partially or wholly integrated.

[0076] The above description is a description of one or more embodiments of the present invention. The present invention is not limited to the specific embodiments disclosed herein, but rather is defined solely by the claims that follow. Furthermore, statements contained in the foregoing description relate to the disclosed embodiments and should not be construed as limitations on the scope of the invention or the definition of terms used in the claims, unless the term or phrase is expressly defined above. Various other embodiments, as well as various changes and modifications to the disclosed embodiments, will be apparent to those skilled in the art.

[0077] As used in this specification and claims, the terms "eg," "for example," "for instance," "such as," and "like," as well as the verbs "comprising," "having," "including," and other verb forms thereof, when used in combination with a list of one or more components or other items, should each be construed as open-ended, meaning that the list should not be considered to exclude other additional components or items. Other terms should be construed using their broadest reasonable meaning unless they are used in a context requiring a different interpretation. Additionally, the term "and / or" should be construed as an inclusive OR. Thus, for example, the phrase "A, B, and / or C" should be construed to cover all of the following: "A"; "B"; "C"; "A and B"; "A and C"; "B and C"; and "A, B, and C."

Claims

1. 1. An aircraft piston engine magneto having a magnetic rotor and an ignition circuit including a charging coil inductively coupled to magnetic poles of the rotor, the charging coil including a plurality of power coils electronically reconfigurable by the ignition circuit between series and parallel connections of the power coils.

2. 10. The magneto of claim 1, wherein the magneto comprises a fully electronically controlled magneto that generates and outputs ignition pulses using an ignition circuit that includes only non-mechanically operated electrical components.

3. 3. The magneto of claim 2, wherein the ignition circuit includes a position sensor disposed adjacent to at least one magnet carried by the rotor, the ignition circuit deriving power and data solely from a rotating magnetic field produced by the rotor during rotation.

4. 1. An aircraft piston engine magneto having a magnetic rotor and an ignition circuit including a reconfigurable charge coil inductively coupled to magnetic poles of the rotor, the reconfigurable charge coil being inductively powered from the magnetic rotor and including a plurality of coils that are electronically reconfigurable from a high-turn, low-current power coil for use during low-speed operation to a low-turn, high-current power coil for use during high-speed operation.

5. 5. The magneto of claim 4, wherein the charging coil is configured as the high turn, low current power coil by electronically connecting the coils in series, and the low turn, high current power coil by electronically connecting the coils in parallel.

6. 6. The magneto of claim 5, wherein the ignition circuit includes a speed detector that detects whether the magnetic rotor, as it rotates, indicates an engine speed above or below a speed threshold, and wherein the ignition circuit configures the plurality of coils in the series connection when the speed detector indicates that the engine speed is below the speed threshold and configures the charge coils in the parallel connection when the speed detector indicates that the engine speed is above the speed threshold.

7. 5. The magneto of claim 4, wherein said ignition circuit includes only non-mechanically operated electrical components, whereby said magneto comprises a fully electronically controlled magneto.

8. 8. The magneto of claim 7, wherein the ignition circuit includes a position sensor disposed adjacent to at least one magnet carried by the rotor, and wherein the ignition circuit derives power and data solely from a rotating magnetic field produced by the rotor during rotation.

9. Housing and a rotor assembly mounted within the housing, the rotor assembly comprising a magnetic rotor and at least one bearing supporting the rotor for rotation within the housing, the rotor assembly having a first end and a second end, the rotor having a permanent magnet assembly disposed between the first end and the second end, the first end being externally accessible at an opening in the housing such that the rotor can be rotationally driven by an external drive component; an ignition circuit comprising circuit components each including at least one power coil and a position sensor inductively coupled to the magnetic rotor, the ignition circuit including a high voltage output terminal mounted in a location accessible from the exterior of the housing; Equipped with the rotor assembly is a terminal mechanical device such that the rotor rotates within the housing without transmitting its mechanical motion to any of the circuit components; Magneto.

10. 10. The magneto of claim 9, wherein the ignition circuit is a fully electronically controlled ignition circuit that uses only non-mechanically operated electrical components within the magneto to generate and distribute ignition pulses to the output terminals.

11. 10. The magneto of claim 9, wherein the ignition circuit comprises a plurality of power coils electronically reconfigurable by the ignition circuit between series and parallel connections of power coils.

12. 1. A piston engine ignition system mechanically powered by a single magnetic rotor and having a plurality of high voltage output terminals adapted to connect to ignition leads to supply ignition energy to one or more spark plugs via the ignition leads, the ignition system comprising a fully electronically controlled ignition circuit operating from power supplied solely via induction from the magnetic rotor, the ignition circuit generating the ignition energy from the received power and selectively distributing the ignition energy as high voltage ignition pulses to the output terminals, the ignition circuit comprising a position sensor detecting the rotational angle of the magnetic rotor, and control logic controlling timing of the ignition pulses relative to the rotational angle of the magnetic rotor as a function of rotor speed based on rotational angle data from the position sensor.

13. 13. The ignition system of claim 12, wherein the control logic further comprises a speed detector that causes a change in ignition timing of the ignition pulse depending on whether the rotor speed is above or below a predetermined speed.

14. 14. The ignition system of claim 13, wherein the speed detector includes timing and logic circuitry that controls the advance and retard of the ignition timing relative to the output of the position sensor, which is indicative of an engine piston being at top dead center (TDC).

15. 15. The ignition system of claim 14, wherein the speed detector sets the ignition timing to a first spark angle when the rotor speed is within a range of approximately 100 rpm to the predetermined speed, and advances the ignition timing to a second spark angle earlier than the first spark angle when the rotor speed is greater than the predetermined speed.

16. 16. The ignition system of claim 15, wherein the first firing angle is approximately 0-10 degrees after TDC, the second firing angle is approximately 18-28 degrees before TDC, and the predetermined speed is within the range of 250-600 rpm.

17. 13. The ignition system of claim 12, wherein the position sensor is a magnetoresistive sensor that outputs the rotational angle data as quadrature sinusoidal waveforms indicative of the rotational angle of the magnetic rotor, and the control circuit includes logic circuitry that uses the sinusoidal waveforms to enable firing of the ignition pulse only during specific rotational angles of the rotor.

18. 13. The ignition system of claim 12, wherein the ignition circuit comprises a plurality of power coils positioned adjacent the magnetic rotor at a first angular position such that the power coils provide the power to operate the ignition circuit, and the position sensor is positioned adjacent the magnetic rotor at a second angular position such that the position sensor senses the magnetic field lines of the magnetic rotor as the rotor rotates.

19. 13. The ignition system of claim 12, wherein the charge coil includes a plurality of power coils electronically reconfigurable by the ignition circuit between series and parallel connections of power coils.

20. 1. A magneto comprising: a permanent magnet rotor; a ferromagnetic core positioned relative to the rotor to concentrate and induce changing magnetic field lines extending between opposing magnetic poles of the rotor as the rotor spins; and an ignition circuit for inductively extracting power from the changing magnetic field lines, the ignition circuit comprising: a power circuit having a reconfigurable charging coil comprising a plurality of power coils wound around the core and providing inductive power to one or more output nodes of the power circuit; a high voltage discharge circuit connected to the output node of the power circuit for generating high voltage spark energy at a plurality of high voltage output terminals; a control circuit connected to at least one of the output nodes of the power circuit and operable under power from at least one of the output nodes of the power circuit, the control circuit including control outputs connected to both the power circuit and a discharge circuit, the control circuit including at least one control output to the power circuit that electronically configures the power coils in either series or parallel, and at least another control output connected to the discharge circuit that causes a high voltage ignition pulse suitable for firing a spark plug; Including, Magneto.

21. 1. A magneto comprising: a permanent magnet rotor; a ferromagnetic core positioned relative to the rotor to concentrate and induce changing magnetic field lines extending between opposing magnetic poles of the rotor as the rotor spins; and an ignition circuit for inductively extracting power from the changing magnetic field lines, the ignition circuit comprising: a power circuit having a plurality of power coils wound around the core and supplying inductive power to one or more output nodes of the power circuit; a capacitive discharge ignition (CDI) discharge circuit having at least one ignition storage capacitor charged via the one or more output nodes, at least one ignition coil configured as a step-up transformer having a primary coil and an inductively coupled secondary coil connected to one or more outputs of a CDI discharge circuit, and at least one controllable solid-state switch, the solid-state switch and primary coil connected in series in circuit across the ignition storage capacitor such that upon activation of the solid-state switch, charge from the ignition storage capacitor flows through the switch and primary coil, thereby establishing a magnetic field that remains until the solid-state switch is deactivated, at which point current through the primary coil is interrupted and a high voltage pulse is induced across the secondary coil; a control circuit including at least one operating power storage capacitor, a position sensor disposed adjacent to the magnetic rotor for detecting magnetic field lines emanating from the rotor as it rotates, and a timing circuit for controlling operation of the solid-state switch based on the rotor angular position sensed by the position sensor; Including, the operating power storage capacitor of the control circuit is connected to the ignition storage capacitor through a diode that allows charging of the operating power storage capacitor and prevents it from being discharged by reverse current to the ignition storage capacitor, whereby the power coil supplies operating power to both the ignition circuit and the control circuit; Magneto.

22. 22. The magneto of claim 21, wherein the control circuit includes at least two dc voltage regulators connected to receive input power from the operating power storage capacitor and output two different dc voltages for logic circuit operation.

23. 22. The magneto of claim 21, wherein said plurality of power coils are electronically reconfigurable by said ignition circuit between series and parallel connections of said power coils.

Images