BACKGROUND
1. Field of the Invention
This invention relates to automobile ignition systems. More specifically, this invention relates to early automobile electronic ignition systems.
2. Prior Art
FIG. 1 depicts an example of an early automobile ignition system. An example of an automobile that used such a system was the Ford Model T. For the purposes of discussion that follows, the term early refers to automobiles produced between the years of 1900 and 1930. The main components of the system comprise commutator 5, coil primary wires 1, 2, 3 and 4, coil box 6 containing four ignition coils, spark plug wires 7, 8, 9 and 10 used to carry high voltage spark to their corresponding spark plugs 14. Note that commutator 5 is sometimes referred to as a Timer.
The basis of operation of this system is 100 year old technology and is well known to those skilled in the art. A brief summary of the essential elements as they pertain to the subject of the present invention will be covered. A simplified schematic diagram for the early ignition system is illustrated in FIG. 2. Ignition switch 18 is closed to provide power from battery 11 to each of the coils 13 contained within coil box 6. Actuation of each coil 13 is controlled by commutator 5 which is physically connected to and operated by the automobile engine CAM shaft that rotates when the engine is cranked. Ignition coils 13 are actuated sequentially by commutator 5 grounding their respective primary windings via wires 1, 2, 3, and 4 to engine ground which is typically connected to the negative terminal of battery 11. Coil actuation results in a self oscillation of primary current resulting in the generation of high voltage pulses on their corresponding secondary winding output. The high voltage pulses from the ignition coil secondary are carried to the respective engine spark plugs 14 via wires 7, 8, 9 and 10. The spark timing must be manually altered by the user as engine speed changes for optimum engine operation. This is accomplished by mechanically rotating commutator 5 with respect to its mounting position on the engine which effectively changes its relation ship to the engine CAM shaft position and hence advances or retards the ignition timing.
FIG. 3 illustrates details of commutator 5. The primary windings of ignition coils are connected to terminals 1, 2, 3 and 4. Each terminal is connected to a corresponding independent electrical contact 6 within the commutator housing. Roller 7 comprises a metal wheel physically and electrically connected to engine CAM shaft 10 that rotates when the engine CAM shaft rotates. Roller 7 functions to provide electrical connection between terminals 6 and the CAM shaft which is also connected to engine ground, most often the negative terminal of the battery 11 of FIG. 2. Ignition coil wires connected to terminals 1, 2, 3 and 4 are thus electrically connected to engine ground sequentially as roller 7 rotates, connecting their respective electrical contact 6 to the CAM shaft ground which is also engine ground. Ignition coil actuation occurs when its respective terminal on commutator 5 is grounded by roller 7 as described previously.
FIG. 4 illustrates an example of prior art that attempts to improve upon the original ignition system of FIG. 2 by eliminating reliance on physical mechanical contact between roller 7 and contact 6 of FIG. 3 in order to actuate ignition coils 13. This is accomplished by replacing the mechanical electrical contacts 6 of FIG. 3 with circuit board 6 containing modern electronic sensors 7 and replacing roller 7 of FIG. 3 with rotor 11 that is still physically attached to engine CAM shaft 10. Rotor 11 contains one or more sensor actuators 9 employed to actuate sensors 7 as they are rotated by the CAM shaft. CAM shaft position sensing is not new or novel. The sensors and sensor actuators may take the form of optical or magnetic or vein. CAM shaft position sensing and operation are well known to those skilled in the art. Electrical contact terminals 1, 2, 3 and 4 are no longer used to actuate ignition coils. Terminals 1 and 2 are used to signal activation of CAM shaft position sensors 7 in response to CAM shaft sensor activators 9. Terminal 4 is used to supply a source of external DC power to sensors 7 and terminal 3 is used to provide connection to engine ground as a DC power return. Hence, the purpose, wiring and operation of commutator 5 is completely different from the original vintage ignition system. A distinct disadvantage of the prior art of FIG. 4 is the use of multiple CAM sensors 7 and multiple CAM sensor activators 9 unless there is a means of compensating differences in sensor to sensor activation times which translates directly to variation in ignition timing which is contrary to the entire purpose of the apparatus.
Operation of the prior art electronic ignition system of FIG. 4 is facilitated with the aid of FIG. 5. Commutator 5 no longer actuates ignition coils 13 directly by providing a path to engine ground, rather, it now functions solely to signal the position of the engine CAM shaft via the former coil primary wires 1 and 2. The other two former coil primary wires 3, and 4 are also no longer used to actuate ignition coils but are now available to feed external DC power to the CAM shaft sensors resident within commutator 5 (see sensors 7 of FIG. 4). Referring to FIG. 5, operation is as follows: Ignition switch 18 is closed to provide system power from battery 11 via battery wire 12 to electronic control module 15 contained within coil box 6 and to power electronic sensors contained in commutator 5 that were previously described with the aid of FIG. 4. Commutator 5 monitors the position of the engine CAM shaft and sends trigger signals via wires 1 and 2 to electronic control module 15 that resides in coil box 6. Electronic control module 15 processes the trigger signals from commutator 5 and turns on semiconductor switches 16 which in turn actuate the firing of coils 13 in synchronization with engine operation. One will note a significant difference in the configuration of FIG. 5 compared to the original prior art of FIG. 2 is that the prior art of FIG. 5 only employs two ignition coils 13 rather than the original four. Engine operation is still possible by exploiting the four stroke cycle of the internal combustion engine; intake, compression, power and exhaust of the four cylinder engine and firing two cylinders in tandem rather than one. The power stroke is fired as usual, however, the other cylinder in the pair is at the end of the exhaust stroke at the time the pair fire which simply does not contribute to the production of engine power. For this reason, this method of engine ignition is well known as the “wasted spark” method to those skilled in the art.
The prior art of FIG. 5 has several disadvantages which are avoided by the present invention. A notable disadvantage is the need to eliminate two of the ignition coils and use of the “wasted spark” method. The wasted spark method is functional but is not benign to engine operation especially during engine starting. The wasted spark firing in the cylinder on its exhaust stroke may in fact fire when at the beginning of the next intake cycle depending upon engine timing. Air and fuel may have already begun to enter cylinder if engine timing is retarded causing a puff back or back fire into the carburetor making it difficult to start. This is of particular disadvantage on a early automobile which relies upon hand cranking to start which can become exhausting. The starting procedure of early hand cranked automobiles requires retarding ignition timing to avoid personal injury from engine kick back which helps guarantee air/fuel mixture has already begun to enter the non-firing cylinder when the “wasted” spark occurs in that cylinder. Another disadvantage of the prior art of FIG. 5 is the need to significantly alter the components of the original system. Coil box 6 of FIG. 5 must be either completely rewired or a pre re-wired module must be installed in place of the original coils 13 to implement the wiring and component swaps. This is undesirable on vintage automobiles which are prized for their original appearance and function. Coil box 6 is easily accessible and inspected to reveal significant modifications have been made to the automobile and it is non-original. Furthermore, substitution of original coils 13 may be necessary to fit all components into coil box 6 result in coil operation that does not mimic original coil operation in which a characteristic “buzz” of the coil primary associated points is heard further diminishing originality.
BRIEF SUMMARY OF THE PRESENT INVENTION
Collection and operation of early automobiles is a popular pursuit that depends upon components that ware with use such as the coil points, roller and timer of the ignition system. Replacement components are becoming increasingly more difficult to find, can be expensive and often are time consuming to replace and align. Parts reproductions are often easily identifiable or alter the performance of the original ignition system degrading the antique value or costing points awarded for originality during automobile shows.
It is the objective of the present invention to offer a solution to this problem by providing a programmable electronic ignition module for early automobiles that utilizes existing components and wiring to retain the look and operation of the original system but with superior performance. The invention replaces the original roller/timer contacts of the original vintage system and actuates the original coils that fire the original spark plugs using the original wiring in the original manor. Electronic ignition module operation is user programmable to emulate the original roller/timer performance or provide automatic spark advance similar to modern automobile operation for optimum power and efficiency while freeing the operator from manual adjustment of spark timing. Ignition module programming is accomplished without any external switches, jumpers or modification to the vintage automobile by simply sensing the presence or absence of ignition coils when power is applied. The electronic ignition module resides fully contained within the confines of the original timer housing without any modifications what so ever, rendering it completely undetectable by visual inspection.
SHORT DESCRIPTION OF THE DRAWINGS
The present invention will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, where in like reference numerals designate corresponding parts in the various drawings, and within:
FIG. 1: Illustrates the fundamental components of the early automobile ignition system.
FIG. 2: Illustrates interconnectivity of the prior art and facilitates the description of its operation.
FIG. 3: Illustrates the inner workings of commutator 5 of FIG. 2 and is used to facilitate the description of its operation.
FIG. 4: Illustrates another example of prior art that provides a means of electronic actuation rather than physical mechanical actuation.
FIG. 5: Illustrates how prior art of FIG. 4 is integrated within in the original system of prior art of FIG. 2.
FIG. 6: Illustrates one embodiment of the present invention that utilizes four sensors and one sensor actuator.
FIG. 7: Illustrates another embodiment of the present invention that utilizes two sensors and two sensor actuators
FIG. 8: Illustrates a detailed schematic diagram of the present invention
FIG. 9: is a detailed schematic diagram showing a modified form of the present invention useful in automobiles that operate on a wider battery voltage range.
DETAILED DESCRIPTION OF THE INVENTION
Referring to FIG. 6, which shows one embodiment of the present invention, commutator housing 5 employs electrical terminals 1, 2, 3 and 4 that are normally isolated from commutator housing 5. Circuit board 6 is mounted within housing 5. Sensors 7 located on circuit board 6 are actuated by sensor activator 9 located on rotor 11 that is physically mounted to engine CAM shaft 10. Operation is as follows: Rotor 11 rotates with engine CAM shaft 11. Sensor activator 9 functions to activate a particular sensor 7 when it moves within close proximity to it. Microcontroller 19 located on circuit board 6 detects actuation of the particular sensor 7 and functions activate a corresponding electronic switch 16 that electrically connects its corresponding terminal 1, 2, 3 or 4 to commutator housing 5 which is also connected to engine ground. Microcontroller 19 determines the mapping between sensor 7 activation and which electronic switch 16 is activated. A typical activation order of electronic switches 16 is to electrically connect terminal 1, 2, 4, and then 3 to commutator housing 5 as CAM shaft rotor 11 rotates clockwise as viewed in FIG. 6. In this case, the present invention just described contained within commutator 5 is a drop in replacement for the prior art commutator 5 of FIG. 2 where coil actuation with respect to CAM shaft position is identical to that described for FIG. 2 with the exception that electronic switching is used as opposed to mechanical switching to activate the ignition coils connected to terminals 1, 2, 3 and 4 with the added requirement that the ignition coil points be electrically bypassed (shorted).
The burden of actuating the ignition coils to produce a continuous series of high voltage sparks when actuated in response to proper alignment of CAM shaft sensor 7 and sensor activator 9 now falls on the electronic ignition module in stead of the ignition coil points and condenser. This is yet another benefit of the present invention as the ignition coil points require careful adjustment and ware out with usage and the condenser often fails in a short circuit rendering the ignition coil useless in the original system. An ignition coil with a shorted condenser is still usable in the electronic ignition system using the present invention since the ignition coil points in which the condenser is connected must be shorted (connected) anyway. It should also be noted that the electronic ignition module has the ability to adjust the duration and duty cycle of the pulses generated by the electronic ignition module to optimize the efficiency and performance of ignition coil 13 operation by microcontroller 19 measuring the voltage applied to the system and applying the appropriate value for ignition coil on (charge) time and off (discharge) time and firing frequency.
It should be understood that the order of activation of electronic switches 16 as rotor 11 turns as well as the mapping of a particular electronic switch 16 to a particular terminal (1, 2, 3 or 4) may be changed to any order. It should also be understood that only two CAM sensors 7 may be employed located 90 degrees with respect to one another with the addition of a second sensor actuator 9 on rotor 11 located 180 degrees in opposition in position as illustrated in the embodiment of the present invention of FIG. 7. Operation of the embodiment of FIG. 7 typically requires actuation of electronic switches 16 to occur in pairs. For example, electronic switches 16 associated with terminals 1 and 4 function to electrically connect terminals 1 and 4 to commutator housing 5 then electronic switches 16 associated with terminals 2 and 3 function to electrically connect terminals 2 and 3 to commutator housing 5 as rotor 11 rotates clockwise. This method of actuation when employed as part of an automobile ignition system is commonly referred to the “wasted spark” method that is well known to those skilled in the art.
In either embodiment of FIG. 6 or 7, the locations of the sensors on circuit board 6 and location of sensor actuators on rotor 11 are orientated to CAM shaft 10 to synchronize rotation and operation with the associated engine to which the CAM shaft is attached.
Note that both embodiments of the present invention illustrated in FIGS. 6 and 7 employ multiple CAM sensors 7 and CAM sensor activators 9 as had some prior art, however, the present invention utilizes microcontroller 19 that is responsive to CAM sensor 7 activation and has the capability of utilizing internally stored sensor calibration information to equalize differences in sensor to sensor activation delay to prevent differences between sensors from translating to variations in ignition timing thereby maintaining precision ignition timing.
FIG. 8 shows a detailed schematic diagram for one embodiment of the present invention. Microcontroller 19 monitors inputs connected to sensors 7 responsible for detecting the position of engine CAM shaft 10 of FIGS. 6 and 7. Microcontroller 11 is also responsible for actuating electronic switches 16 in the proper sequence for a particular duration. Electronic switches 16 connect their respective electrical terminals 1, 2, 3 and 4 to circuit ground 17 which is electrically connected to commutator housing 5 of FIGS. 6 and 7.
A unique and novel aspect of the present invention is the method in which it is powered. Terminals 1 and 2 are connected to the positive terminal of battery 11 via their associated ignition coil 13 primary winding, wire 12 and ignition switch 18. Although each coil 13 primary winding is periodically switched to circuit ground 17 via corresponding electronic switch 16 to actuate corresponding spark plug 14, they are never simultaneously switched to ground at the same instance of time. In this way, power from battery 11 is always available from either terminals 1 or 2 and at times from both terminals 1 and 2. The circuit is also designed to be immune to the resulting high voltage transients produced by actuating associated ignition coils 13 in the generation of spark.
Powering the electronic ignition circuitry in this way preserves the original automobile wiring, interconnectivity and function without modification. Diodes 8 prevent loading from terminal 1 or 2 when either terminal is switched to ground to fire its corresponding ignition coil 13. Diodes 8 also provide a source of DC power from either terminal 1 or 2 when they are not being switched to ground when their associated ignition coils 13 are not being activated. Together, diodes 8 provide an un-interrupted source of DC power for circuit operation since terminals 1 and 2 are never switched to ground simultaneously. Resistor 7 limits the current to Zener diode 6 which provides a source of regulated voltage to operate microcontroller 19 and all other electronic components. Zener diode 6 also protects the power supply from high positive voltage and negative voltage spikes generated by its associated ignition coil 13 activation. Capacitor 5 filters out any voltage variation caused when switching between voltage sources supplied from terminals 1 or 2.
Another unique and novel aspect of the embodiment of FIG. 8 is the way microcontroller 19 can be programmed by the user to function in different modes without the need for any external switches, buttons, jumpers or modification to the original automobile wiring preserving its originality. Programming is accomplished by sensing the presence or absence of ignition coils during power up, that is: closure of ignition switch 18. Terminals 3 and 4 connected to their respective ignition coil 13 primary provide a source of power via battery wire 12 connected to the positive terminal of battery 11 via ignition switch 18. Microcontroller 19 can check if a coil is present or absent by checking the voltage level on its respective terminal 3 and 4. Voltage on terminal 3 is present if its associated coil is present and is connected to the circuit. Voltage on terminal 3 is not present if it its associated coil is not present and is disconnected from the circuit. Likewise, voltage on terminal 4 is present if its associated coil is present and is connected to the circuit. Voltage on terminal 4 is not present if it its associated coil is not present and is disconnected from the circuit. In this way, microcontroller 19 can use the presence or absence of ignition coils during power up to determine which program options are to be used when the program runs.
Using this example involving the presence of absence of two coils, four programming scenarios are possible. Microcontroller 19 can be programmed to execute a default program if both coils associated with terminals 3 and 4 are present (connected) causing power to be present on both terminals 3 and 4 when power is applied via ignition switch 18. Microcontroller 19 can be instructed to execute an alternate program if there is no voltage present on terminal 4 only when power is applied resulting from the user removing its associated coil 13 from the circuit prior to applying power via ignition switch 18. The user may reprogram which program executes, the default or alternate program, when power is applied by removing voltage from terminal 3 during power up by removing coil 13 associated with terminal 3 prior to closing ignition switch 18. The specific program to serve as the default program can be changed by microcontroller sensing the voltage level on terminal 4 when ignition switch 18 is closed and power is applied. Voltage will be present on terminal 4 if its associated ignition coil 13 is present and connected to the circuit. Voltage will be absent on terminal 4 if its associated ignition coil 13 is absent and disconnected from the circuit. The purpose of resistor 10 and Zener diode 9 is to regulate the voltage presented to microprocessor 19 from terminals 3 and 4 to safe logic voltage levels and to protect microprocessor 19 from high voltage or negative voltage spikes produced as a result of actuation of ignition coils 13 associated with terminals 3 and 4.
Microcontroller 19 can execute a default program that mimics the original ignition system of the early automobile by actuating ignition coils 13 of FIG. 8 as long as sensor actuator 9 of FIG. 6 remains in close proximity of its corresponding sensor 7 of FIG. 6. Microcontroller 19 can also execute an alternative program that delays actuation of coils 13 when sensor actuator 9 of FIG. 6 remains in close proximity of its corresponding sensor 7 of FIG. 6. The delayed activation can be varied depending upon the CAM shaft rotational velocity to provide less delay as the revolutions per minute (RPM) increase effectively advancing the spark timing with engine speed as is well known and commonly done in modern automobile ignition systems.
FIG. 9 shows a detailed schematic diagram for an alternate embodiment of the present invention useful in operating over a broad operating voltage range. Microcontroller 19 monitors inputs connected to sensors 7 responsible for detecting the position of engine CAM shaft 10 of FIGS. 6 and 7. Microcontroller 11 is also responsible for actuating electronic switches 16 in the proper sequence for a particular duration to actuate corresponding ignition coil 13 and corresponding spark plug 14. Electronic switches 16 connect their respective electrical terminals 1, 2, 3 and 4 to circuit ground 17 which is electrically connected to timer housing 5 of FIGS. 6 and 7 as was described previously.
The way the circuit of FIG. 9 is powered is again unique and novel as it receives power from the same terminals used to actuate the primary of ignition coils 13 yet the circuit is designed to be immune to the resulting high voltage transients associated with actuating associated coil 13 in the generation of spark. Terminals 1 and 2 are connected to the positive terminal of battery 11 via their associated ignition coil 13 primary winding via wire 12 and ignition switch 18. Although each coil 13 primary winding is periodically switched to circuit ground 17 via corresponding electronic switch 16, they are never simultaneously switched to ground at the same instance of time. In this way, power from battery 11 is always available from either terminals 1 or 2 and at times from both terminals 1 and 2. Microcontroller 19 of this embodiment of the invention controls from which terminal 1 or 2 power is to be supplied since microcontroller 19 also controls when terminals 1 and 2 are switched to ground via corresponding electronic switch 16 to actuate their associated ignition coil 13 and associated spark plug 14. Microcontroller 19 selects power from the terminal not being used to actuate its associated coil 13 by turning on its associated electronic switch 32 which in turn turns on its corresponding electronic switch 8 to provide power to voltage regulator 37 which then provides conditioned power to microcontroller 19 via schottky diode 5. Capacitor 6 filters out any voltage ripple present and associated resistor 31 limits the current flow through electronic switch 8 to a safe value. Microcontroller 19 functions to turn off the source of power from terminal 1 or terminal 2 which is switched to ground via its associated electronic switch 16 by turning off the terminals associated electronic switch 32 and its associated electronic switch 8 cutting off the supply of power from that particular coil terminal effectively isolating it from the input of voltage regulator 37 when it is activating its associated ignition coil 13. This operation functions to protect voltage regulator 37 from the high voltage transients resulting from the actuation of the terminal's associated coil 13 and prevents voltage regulator 37 from loading down the associated terminal being used to actuate its associated ignition coil 13 which would otherwise compromise the generation of sufficiently high voltage necessary to operate its associated spark plug 14.
An initial source of power must be provided to microcontroller 19 before it can take over managing control of its power source as just described. This is accomplished from terminal 1 by resistor 35 and Zener diode 34 as was similarly done in the embodiment of FIG. 8 to provide a regulated source of power while the current draw requirement is low. Electronic switch 33 is added to automatically disconnect this temporary source of power once microcontroller takes over managing control of its power source when power becomes available at the output of voltage regulator 37 as was described previously. Schottky diode 5 isolates temporary power source provided by resistor 35, Zener diode 34 and electronic switch 33 from being loaded down from microcontroller operated voltage regulator 37 before it becomes operational. Electronic switches 8 are capable of withstanding high voltages that effectively isolate their associated terminals 1 and 2 that are subjected to high voltage and negative spikes when they are used to actuate their respective ignition coil 13. Powering the electronic ignition circuitry in this way also preserves the original automobile wiring, interconnectivity and function without modification. The embodiment of FIG. 9 can also be programmed by the presence or absence of ignition coils 13 during power up; closure of ignition switch 18 as was described in detail for the embodiment of FIG. 8.
Another unique feature of the embodiment of FIG. 9 is the ability of microcontroller 19 to sense the value of battery voltage applied to the system via terminal 3 by the voltage divider formed by series resistor 10 and shunt resistor 36 utilizing the Analog to Digital Converter (ADC) input feature of microcontroller 19. This is a critical need if the battery voltage deviates from the nominal value, typically 12V. This is because the time needed to charge the associated ignition coils 13 changes as the battery voltage is varies. Early automobiles operated from battery voltages from 6 volts to 12 volts typically in 2 volt increments (6, 8, 10 or 12V). The software program operating microcontroller 19 utilizes knowledge of the supply voltage to select the proper coil charge time and discharge time for optimal ignition system performance without any input from the operator.
It should be understood that in either embodiment of the invention of FIG. 8 or FIG. 9, microcontroller 19 can be programmed to map actuation from camshaft sensors 7 to actuation of associated ignition coil 13 in different ways. One desirable way to map actuation is to commence of ignition coil 13 actuation as soon as the associated camshaft sensor 7 is activated and continue ignition coil 13 actuation until the associated camshaft sensor 7 ceases activation. This method of activation mimics the original operation of ignition system employed by early automobiles by the roller/contact. This example of mapping camshaft sensor activation to associated ignition coil actuation may be the default program executed by microcontroller 19 when power is applied and is not changed by the absence of any ignition coils 13. Another desirable method to map actuation of camshaft sensors 7 to associated ignition coils 13 is to acknowledge activation of camshaft sensor 7 and delay actuation of its associated ignition coil 13 for a predefined interval that is dependant upon the frequency of activation of camshaft sensors 7 which is indicative of engine Revolutions Per Minute (RPM). This method of mapping camshaft sensor 7 to associated ignition coil 13 can be used to advance ignition timing as engine RPM increases to obtain optimum engine power and efficiency. This automatic timing advancement method of mapping camshaft sensor 7 to associated ignition coil 13 may be the non-default, alternate, program executed by microprocessor 19 when one ignition coil 13 is removed from the circuit when power is first applied.
It will be understood that this invention is not limited to the examples given herein by way of illustration, but only by the scope of the appended claims.
Patent Application
20110126802
