ENGINE KILL SWITCH AND CONTROL ASSEMBLY
A speed regulating circuit in communication with an ignition circuit having a primary coil coupled to an ignition member to cause an ignition event within an engine, the speed regulating circuit being arranged to selectively prevent energy from the primary coil from being discharged to the ignition member to selectively prevent an ignition event. In at least some implementations, the speed regulating circuit includes a bidirectional or bilateral triode thyristor having an anode coupled to the primary coil and an anode coupled to ground, and an input gate that may be selectively actuated to route to ground energy received at the triode thyristor from the primary coil to inhibit transfer of energy from the primary coil to the ignition member. The triode thyristor may be selectively actuated, for example, as a function of engine speed, such as an engine speed above a threshold speed.
This application is a divisional of U.S. patent application Ser. No. 16/072,309 filed on Jul. 24, 2018 which is a National Phase Application of PCT/US2017/014057 filed on Jan. 19, 2017 and claims the benefit of U.S. Provisional Application Nos. 62/364,348 filed on Jul. 20, 2016 and 62/286,691 filed on Jan. 25, 2016. The entire contents of these priority applications are incorporated herein by reference in their entireties.
TECHNICAL FIELDThe present disclosure relates generally to internal combustion engines and more particularly to control systems for such engines.
BACKGROUNDSmall or utility internal combustion engines are used to power a wide variety of various products such as electric generators, air compressors, water pumps, power washers, lawn and garden equipment such as garden tractors, tillers, chain saws, leaf blowers, lawn mowers, lawn edgers, grass and weed trimmers, and the like. Many of these engines are single cylinder two-stroke or four-stroke and gasoline powered with a spark plug and an ignition control module connected by two wires to the terminals of an engine stop or kill switch. The kill switch is manually operable by an operator to terminate supplying an electric current to the spark plug and thus stopping operation of a running engine. Typically these products do not have a separate battery for supplying an electric current to the spark plug and instead utilize a magneto system with magnets mounted on a flywheel of the engine to generate electric power for a capacitive discharge ignition system which often includes a microcontroller which typically varies and controls ignition timing of the current at a high potential voltage supplied to the spark plug of the operating engine. Typically these engines are manually cranked for starting by an automatic recoil rope starter.
SUMMARYIn at least some implementations, a kill switch assembly includes an electric switch manually operated by an operator to provide an engine kill or stop signal to the ignition control system of an operating engine and circuitry for performing at least one additional function such as receiving engine performance data from its microcontroller to be stored in a kill switch microcontroller, sending data to or receiving data from a computer, sending temperature information to the engine microcontroller, receiving a signal from the engine microcontroller to provide a visually observable signal to the product operator, receiving a signal from an external control circuitry for sending a signal to the engine microcontroller to initiate a routine or process programmed therein, and the like.
In at least some implementations, a kill switch assembly for an internal combustion engine with an engine microcontroller includes a housing, a first terminal carried by the housing and configured for connection to a ground, a second terminal carried by the housing and configured for connection to an engine microcontroller, and an electric kill switch carried by the housing, electrically connected to the first and second terminals, and manually operable by an operator to change the state of the electric switch to provide an engine stop signal to the engine microcontroller. The assembly may also include an electronic circuit carried by the housing, connected to the first and second terminals, and communicating with the engine microcontroller. In at least some implementations, the communication may occur wirelessly, such as via bluetooth protocol.
A speed regulating circuit in communication with an ignition circuit having a primary coil coupled to an ignition member to cause an ignition event within an engine, the speed regulating circuit being arranged to selectively prevent energy from the primary coil from being discharged to the ignition member to selectively prevent an ignition event. In at least some implementations, the speed regulating circuit includes a bidirectional or bilateral triode thyristor having an anode coupled to the primary coil and an anode coupled to ground, and an input gate that may be selectively actuated so that energy received at the triode thyristor from the primary coil PRI is routed to ground thereby inhibiting or preventing transfer of energy from the primary coil to the ignition member. In at least some implementations, the input gate may be coupled to a microcontroller that selectively actuate the triode thyristor as a function of engine speed, for example, an engine speed above a threshold speed.
The following detailed description of certain embodiments and best mode will be set forth with reference to the accompanying drawings, in which:
Typically, this engine does not have any battery supplying an electric current to the spark plug or powering the control module 28 which typically includes a microcontroller. Typically, this engine is manually cranked for starting with an automatic recoil rope starter.
The term “light-duty combustion engine” broadly includes all types of non-automotive combustion engines including two and four-stroke gasoline powered engines used in various products including portable electric generators, air compressors, water pumps, power washers, snow blowers, personal watercraft, boats, snowmobiles, motorcycles, all terrain vehicles, lawn and garden equipment such as garden tractors, tillers, chainsaws, edgers, grass and weed trimmers, air blowers, leaf blowers, etc.
As shown in
The stator assembly 168 may include a lamstack 170 having a first leg 172 and a second leg 174 (separated from the rotating flywheel by a relatively small and measured air gap which may be about 0.3 mm), a charge coil winding 176, an ignition primary coil winding 178 and a secondary coil winding 180 which may all be wrapped around a single leg of the lamstack. The lamstack 170 may be a generally U-shaped ferrous armature made from a stack of iron plates and may be in a module housing located on the engine. The ignition primary and secondary coil windings 178, 180 may provide a step-up transformer and as is well known by those skilled in the art, the primary winding 178 may have a comparatively few turns of a relatively heavy gauge wire, while the secondary ignition coil winding 180 may have many turns of a relatively fine wire. The ratio of turns between the primary and secondary ignition windings generates a high voltage potential in the secondary winding that is used to fire the spark plug 30 of the engine 22 to provide an electric arc or spark and consequently ignite an air-fuel mixture in the engine combustion chamber.
As shown in
The microcontroller 188 may include a memory 198 which can store a look-up table, algorithm and/or code to determine and vary the engine ignition timing relative to top dead center of the piston in the cylinder for various engine operating speeds and conditions. In some applications, the microcontroller 188 may also vary and control the fuel-to-air ratio of the air-and-fuel mixture supplied to the cylinder of the operating engine in response to various engine operating speeds and conditions. Various microcontrollers or microprocessors may be used as is known to those skilled in the art. Suitable commercially available microcontrollers include Atmel ATtiny series and Microchip PIC 12 family. Examples of how microcontrollers can implement ignition timing systems can be found in U.S. Pat. Nos. 7,546,846 and 7,448,358, the disclosures of which are incorporated herein by reference. The memory 198 may be a reprogrammable or flash EEPROM (electrically erasable, programmable read-only memory). In other instances, memory 198 may be external of and coupled to the microcontroller 188. The memory 198 should be construed broadly to include other types of memory such as RAM (random access memory), ROM (read-only memory), EPROM (erasable, programmable read-only memory), or any other suitable non-transitory computer readable medium.
As shown in
Pin 3 is a general purpose input or output program port which is not used. Pin 4 is a ground which is connected to the circuit ground.
Pin 6 is a signal input connected to the charge winding 176 via resistors 218 and 220, zener diode 222, and capacitor 224 to receive an electronic signal representative of the position of an engine piston in its combustion chamber usually relative to the top dead center (TDC) position of the piston. This signal can be referred to as a timing signal. The microcontroller 188 can use this timing signal to determine engine speed (RPM), the timing of an ignition pulse relative to the piston(s) TDC position (usually from a look-up table), and whether or not and, if so, when to activate an ignition pulse.
Pin 7 is an output signal pin which is connected to input pin 5 through resistors 226 and 228. So that pin 5 is not affected by noise and radio frequency interference (RFI) produced by the spark plug 30, pin 5 is also connected through a capacitor 230 to the circuit ground 196.
In use, the spade connector terminal 72 of the kill switch 64 is connected to the ground 196 of the circuit. The other connector spade terminal 70 of the kill switch is connected to the junction 232 between the first and second resistors 226 and 228. Preferably the first resistor 226 has a resistance value which is in the range of 2 to 20 kOhms, desirably 2 to 12 kOhms, and preferably 2 to 4 kOhms. Desirably, the second resistor 228 has a resistance value in the range of 2 to 2.5 kOhms and preferably 2.2 kOhms. Preferably, the capacitor 230 has a capacitance of about 1 nanofarad.
When the engine is operating, the microcontroller 188 is powered up to receive a signal through pin 6 from which it determines the engine speed or RPM and the position of the piston normally relative to top dead center. Through pin 3, the microcontroller controls the state of the SCR switch 186 to charge the capacitor 184, and typically uses a look-up table stored in memory 198 to determine ignition timing, and changes the state of the ignition switch 186 to discharge the capacitor to produce a spark or arc in the gap of the spark plug 30 to initiate combustion of the fuel-to-air fuel mixture in the engine cylinder. When the kill switch 64 is open (as shown in
Whenever the kill switch 64 is closed, the input at pin 5 is zero volts which the microcontroller interprets as a command to shut down the engine and “turns on” and “holds on” the ignition switch 186 to prevent further high potential voltage pulses being supplied to the spark plug 30 and thus terminating ignition of the fuel mixture in the cylinder until the engine stops or ceases operation.
In accordance with a feature of this invention, a kill switch assembly 60 has a circuit board 62 and an engine kill switch 64 both in the same housing 66. Preferably, housing 66 is mounted in the same location 68 in the handle housing as a conventional engine kill switch. This kill switch assembly 60 has two preferably spade connector terminals 70, 72 one of which is connected to a ground wire 74 and the other is connected to a an engine module communication wire 76 for the purposes of the circuitry of the assembly 60 communicating through these wires with the microcontroller 188 of the engine module 28 and to send another signal to kill or stop the running engine when the operator manually actuates a rocker button 78 of the kill switch 64 to stop operation of the engine. In prior art trimmers and the like, a manually actuated conventional rocker switch only provides a signal to kill or stop the operating engine typically by a control circuit microcontroller discontinuing or stopping the application of the high potential voltage to the spark plug so that it does not ignite any air-fuel mixture in the engine cylinder. The kill switch housing 66 is electrically non-conductive and insulative and may be a plastic housing.
As shown in
As shown in
The functions and features of the kill switch circuitry may also be transmitted wirelessly, received wirelessly or both, as shown in
Providing the wireless communication module near the kill switch 64 or as part of the kill switch assembly may improve the operation of the device, at least in applications wherein the kill switch is located remotely from and not on or immediately adjacent to the engine and/or flywheel which may create EMF interference that makes detection of transmitted signals more difficult. For example, in the application of a weed trimmer or lawn edger, the kill switch may be provided on a handle that is spaced 6 inches or more from the engine or flywheel. Locations closer to the engine may also be used, but signal detection may be more difficult because of interference associated with such locations.
A control circuit 500 of
The speed regulating circuit 502 is configured to selectively prevent energy at the primary coil (PRI) from being discharged which in turn would otherwise create a spark at the ignition member (e.g. a spark plug). In the current embodiment, the speed regulating circuit 502 includes the microprocessor 510 coupled at pin 5 to an input gate of a bidirectional or bilateral triode thyristor 512 (sometimes called a TRIAC) via a resistor 514. The anodes of the TRIAC are coupled to the primary coil (PRI) and to system ground (GND), respectively. Thus, when the microprocessor 510 selectively actuates or triggers the input gate of the TRIAC 512, energy received at the TRIAC from the primary coil PRI is driven to ground GND, thereby inhibiting sparking at the spark plug and consequently slowing the engine speed. Later, the microprocessor 510 may selectively actuate higher engine speed by ceasing to actuate or trigger the TRIAC gate; consequently, primary coil energy PRI will not be driven to ground GND, the spark plug will fire again, and the engine speed will increase.
In the present implementation, the microprocessor 510 also receives data associated with the speed of the engine via pin 6—pin 6 being coupled to AC_IN (or node N1) via resistor 516. Using the voltage (or current) received at pin 6 and a known value of resistor 516, the microprocessor 510 is configured to calculate current engine speed. Thus, when the engine speed exceeds a desired maximum threshold, the microprocessor 510 selectively may trigger the TRIAC 512 to dump power to ground GND. Likewise, when the microprocessor 510 determines the engine speed has fallen below a desired minimum threshold, the microprocessor 510 may cease triggering the TRIAC 512 so that the TRIAC no longer drains power to GND.
In at least one embodiment, the power circuit 504 includes a diode 520, a transistor 522 (e.g., a PNP transistor having emitter E, collector C, and base B), and a protection circuit 524. The emitter E is coupled to both pin 8 (or mGND) of the microprocessor 510 and a capacitor 526 (which in turn is coupled to node N3 or ground GND). In this circuit embodiment, pin 8 (mGND) may be some negative voltage (e.g., approximately −4V), while pin 1 (Vcc or GND) may be approximately 0V.
The collector C is coupled between a resistor 528 and an anode of diode 520—a cathode of the diode 520 being coupled to node N1. Base B (node N2) is coupled to an opposite end of resistor 528 and also a cathode of a thyristor 530 of circuit 524. In operation, current may flow through the emitter E and base B (and ultimately diode 520) during negative portions of the AC signal—e.g., drawn through diode 520 by the AC signal. And in general, capacitor 526 becomes charged by the AC signal and the voltage of capacitor 526 serves as the input voltage to pin 8 of the microprocessor 510. Consequently, the microprocessor 510 may be configured to thereby provide a negative voltage trigger signal to the TRIAC 512. A negative trigger at the TRIAC may enable the TRIAC to pass through to ground GND both positive and negative portions of the AC voltage received at the primary coil PRI; if the TRIAC 512 were triggered by a positive voltage, then, in some implementations, both positive and negative portions of the AC voltage might not be shorted.
Protection circuit 524 includes the thyristor 530, a zener diode 532, and the capacitor 526. A cathode of the zener diode 532 is coupled to ground GND (or node N3), whereas an anode thereof is coupled to an input gate of the thyristor 530 (via a resistor 536) so that when the voltage across zener diode 532 exceeds the so-called breakdown voltage or threshold, the thyristor 530 is triggered. In operation, when the charge on the capacitor 526 exceeds the breakdown threshold (e.g., about −4V), then the thyristor 530 is triggered and current can flow through the thyristor 530 (anode to cathode), thereby inhibiting further charge on capacitor 526. During this time, the charge of capacitor 526 may not charge, but may drain—e.g. powering the microprocessor 510 until the voltage of capacitor 526 is less than the breakdown voltage, at which time the thyristor 530 once again may inhibit current flow (anode to cathode)—e.g., the thyristor 530 may be a “gate turn-off” or GTO thyristor. Thus, the power circuit 504 provides power to the microprocessor 510, and the protection circuit 524 prevents the microprocessor 510 from a potentially damaging overvoltage scenario.
The clock circuit 506 includes an external oscillator 540 coupled to the microprocessor 510 at pins 2, 3 and 8 for improved clocking to aid in detecting engine speed, although this arrangement is optional and may be omitted (see for example
The programming circuit 508 is configured to tune the microprocessor 510 to operate with a different desired engine speed. For example, currently the microprocessor 510 will trigger the TRIAC 512 at a predetermined engine speed; however, in some embodiments a different predetermined engine speed may be desired instead. Thus, circuit 508 enables programmability of the engine speed used to trigger the TRIAC 512. The programming circuit 508 is optional and also may be omitted.
As discussed above, the microcontroller 510 may provide a negative voltage to the gate of the TRIAC 512 when it is desired to prevent a spark event which prevents a combustion event within the engine and has the effect of reducing engine power and speed. The microcontroller 510 may monitor engine speed as a function of AC_IN signal generated by magnets associated with the engine flywheel. When an engine speed above a threshold is determined, the output may be provided to the TRIAC gate to short the primary coil PRI and pass energy therein to ground, and this is accomplished without a battery and without a relay which can be expensive and not reliable over time. The engine speed may be limited in this way for any desired reason, including prevention of damage to the engine or otherwise. The primary coil PRI may be grounded in this way for all or any at least some engine cycles (e.g. every 1 out of 3 cycles or the like) until the engine speed is at or below the threshold speed, or until some other engine speed is attained, as desired.
As illustrated in
Circuit 500′ may include additional features as well. For example, circuits 560, 562 are adapted to provide filtering characteristics to improve operation of the microprocessor 510 (e.g., smoothing the AC signal, minimizing undesirable noise, etc.). For example, circuit 560 includes a resistor and capacitor arranged in parallel between node N5 (which powers the microprocessor at pin 8) and node N6 (e.g., pin 1 (Vcc) or GND). Similarly, circuit 562 includes a resistor and capacitor arranged in parallel between node N5 and node N7 (which is coupled to pin 6 of the microprocessor 510 and also node N1 (via resistor 516)). These filtering circuits may or may not be required in all embodiments.
While the forms of the invention herein disclosed constitute presently preferred embodiments, many others are possible. It is not intended herein to mention all the possible equivalent forms or ramifications of the invention. It is understood that the terms used herein are merely descriptive, rather than limiting, and that various changes may be made without departing from the spirit or scope of the invention.
Claims
1. A speed regulating circuit in communication with an ignition circuit having a primary coil coupled to an ignition member to cause an ignition event within an engine, the speed regulating circuit arranged to selectively prevent energy from the primary coil from being discharged to the ignition member to selectively prevent an ignition event, wherein the speed regulating circuit includes a bidirectional or bilateral triode thyristor having an anode coupled to the primary coil and an anode coupled to ground, and an input gate that may be selectively actuated so that energy received at the triode thyristor from the primary coil PRI is routed to ground thereby inhibiting or preventing transfer of energy from the primary coil to the ignition member.
2. The circuit of claim 1 wherein a microcontroller is communicated with the input gate to control actuation of the triode thyristor.
3. The circuit of claim 2 wherein the triode thyristor is actuated when the engine speed is above a threshold speed.
4. The circuit of claim 1 which also includes a charge coil adapted to have induced therein an alternating current, and a microcontroller coupled to the charge coil and powered by a negative portion of the alternating current, and wherein the microcontroller provides a negative voltage signal to the input gate of the triode thyristor.
5. The circuit of claim 2 which includes a charge coil adapted to have induced therein an alternating current, and a power circuit, the power circuit includes a capacitor, a diode and a transistor, wherein an emitter of the transistor is coupled to both the microcontroller and a capacitor, a collector of the transistor is coupled between a resistor and the diode, and a base of the transistor is coupled to the resistor, and wherein, negative portions of the alternating current flow through the emitter and the base and the capacitor is charged by the negative portions of the alternating current, and wherein the capacitor is coupled to the microcontroller to power the microcontroller.
6. The circuit of claim 5 wherein the microcontroller provides a negative voltage signal to the input gate of the triode thyristor.
7. The circuit of claim 6 wherein the triode thyristor is arranged to pass through to ground both positive and negation portions of the alternating current.
8. The circuit of claim 2 which includes a kill switch that is coupled to the microcontroller and when the kill switch is actuated the microcontroller actuates the triode thyristor to prevent at least one ignition event.
9. The circuit of claim 8 wherein the kill switch is coupled to ground and two resistors that are coupled to different inputs of the microcontroller.
10. The circuit of claim 9 wherein the resistors are arranged as a voltage divider.
11. The circuit of claim 1 which includes an alternating current signal input and wherein the anode coupled to the primary coil is coupled to the alternating current signal input and not directly to the primary coil.
Type: Application
Filed: Oct 20, 2020
Publication Date: Feb 4, 2021
Inventors: Martin N. Andersson (Caro, MI), Cyrus M. Healy (Ubly, MI), Gerald J. LaMarr, JR. (Bay City, MI), George M. Pattullo (Caro, MI)
Application Number: 17/074,698