The present disclosure relates generally to internal combustion engines and more particularly to a control system with a remote sensor of the throttle valve position of a carburetor or other device supplying a fuel and air mixture to a small engine.
Small internal combustion engines are used to power a variety of various products such as chain saws, leaf blowers, lawn mowers, edgers, grass and weed trimmers, and the like. Many of these engines are single cylinder two-stroke or four-stroke gasoline powered internal combustion engines having a carburetor or other device with a throttle valve controlling the fuel and air mixture supplied to the operating engine. Many of these products have a manually movable throttle lever or trigger remote from the throttle valve that controls the opening and closing of the throttle valve and in close proximity a kill switch connected to an ignition control module by two terminals and two wires so that closing of the normally open kill switch causes the ignition module to terminate supplying an electric current to a spark plug of the engine and thus stopping operation of the engine. Typically, these engines 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 the flywheel to generate power for a capacitive discharge ignition system of the module which typically also varies and controls ignition timing of the current at a high potential voltage supplied to the spark plug. Typically, these engines are manually cranked for starting with an automatic recoil rope starter.
For many engine control systems, it would be desirable to sense when the throttle valve is near or at its wide open throttle (WOT) position for one or more of a variety of purposes including without limitation initiating automatic or self-adjustment of the ratio of fuel-to-air in the mixture, cancelling a centrifugal clutch engagement limiter feature when the operator advances the throttle valve from fast idle or idle to a wide open throttle (WOT) position, initiating active engine acceleration such as by advancing ignition timing and/or fuel enrichment of the fuel-air mixture supplied to the engine, activating engine rapid comedown enhancement from WOT to idle such as by retarding ignition timing and enleaning fuel in the fuel-air mixture, etc.
In at least some implementations, an electric switch may be in a location remote from an engine throttle valve, such as in the control handle of a handheld product, will change state such as by movement of a throttle lever or trigger carried by the control handle when the trigger is moved near to or at its WOT position. In at least some implementations, this electric switch and related circuitry may use the same two wires utilized by a conventional kill switch to stop operation of the engine. In at least some implementations, both the throttle position and kill switches may be in the same housing and may use the same terminals to connect with the same two wires to connect both switches with a microcontroller of an engine ignition control module.
In at least some implementations, a control module for a spark ignited engine with a remote trigger of a throttle lever may include a microcontroller controlling the spark initiated combustion of an air-fuel mixture, an engine kill switch remote from the engine and connected by one of a pair of wires to the microcontroller to stop engine operation when manually actuated to change the state of a pair of its contacts, and a throttle lever position sensor switch remote from the engine throttle valve and connected by the other of the same pair of wires to the microcontroller to signal when the trigger is moved to near or at its wide open throttle position.
The following detailed description of preferred 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 which typically includes a microcontroller. Typically, this engine is manually cranked for starting with an automatic recoil rope starter.
This engine typically has a carburetor with a throttle valve, controlling the supply of an air-fuel mixture for starting and operating the engine. In lieu of a carburetor, some engines may have an air intake with a throttle valve controlling air flow into the engine and a fuel injector or other device injecting fuel into either the air flow or directly into the cylinder of the internal combustion engine. The fuel injector or other device is controlled by circuitry of a module to supply the desired quantity of fuel for varying engine operating conditions.
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 devices or products including lawn and garden equipment, lawn mowers, snow blowers, personal watercraft, boats, snowmobiles, motorcycles, all terrain vehicles, and a variety of handheld power tools including grass and weed trimmers, edgers, chain saws, air blowers, leaf blowers, etc.
As shown in
In accordance with a feature of this invention, a dual switch assembly 60 has a throttle lever position sensor switch 62 and an engine kill switch 64 preferably, but not necessarily, 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 dual 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 module communication wire 76 for the purposes of sending through these wires and to the module 28 one signal when the throttle lever 38 is near or at its WOT position and another signal to kill the 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 switch housing 68 is electrically non-conductive and insulative and may be a plastic housing.
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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 model ATTINY and Microchip model 12F. 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 70 of the dual switch 60 is connected to the ground 196 of the circuit. The other connector spade terminal of the dual switch is connected to the junction 232 between the first and second resistors 226 and 228. Preferably the first resistor 226 and the resistor 148 in the sensor switch 62 have the same resistance value which is in the range of 1 to 10 kOhms, desirably 1 to 6 kOhms, and preferably 1 to 4 kOhms. Desirably, the second resistor 228 is 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 both of the switches 62 and 64 of the dual switch 60 are open (as shown in
When the throttle lever 38 returns from its WOT position to its part throttle or idle position, the throttle position switch 62 is opened and as long as the kill switch 64 is open, the input to microcontroller pin 5 is again an alternating zero volts and 5 volts and the microcontroller interprets this condition as meaning that the carburetor throttle valve 34 is not at or near its wide open position. If desired, from this change of condition and the engine speed input signal at pin 6, the microcontroller can determine whether the engine is in a rapid comedown or de-acceleration mode and if so initiate a deceleration sequence such as changing the ignition timing and/or increasing or decreasing the fuel supplied to the engine cylinder.
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.
The microcontroller may utilize the signal that the carburetor throttle valve is in its wide open position for one or more of a variety of purposes including without limitation changing the ignition timing, initiating an engine control cycle to assist in acceleration of the engine from an idle or part throttle operating state to a wide open throttle operating state which may include advancing the ignition timing and/or enriching the fuel-air mixture supplied to the engine combustion chamber, cancelling a centrifugal clutch engagement limiter feature when the operator advances the carburetor throttle valve from an idle or a fast idle position to WOT position, activating an engine rapid comedown from WOT to idle enhancement feature such as by retarding ignition timing and/or enleaning or enrichening the air-fuel mixture or cutting off the fuel supplied to the engine during the rapid comedown, or for the other engine or product control purposes for which it is desirable to know whether or not the carburetor throttle valve is at or near WOT.
Connecting the same two switch connector terminals, to the contacts of both the throttle position sensor switch and the engine kill switch enables use of the same two wires and connector terminals which otherwise would be required for a conventional kill switch alone, provides a low cost sensing of when the carburetor throttle valve is at or near its fully open or WOT position. Locating the throttle position sensor switch remote from the carburetor and engine, such as in the control handle of a handheld power device provides a clean environment in which this sensor switch is not subjected to dust, dirt, accumulated fuel and/or oil, engine heat and the like. Detaching the throttle position sensor switch from the engine and the carburetor and spacing this switch at least 2″ away from the engine usually prevents this switch from being overheated by the operating engine.
The remote location of the throttle position sensor switch eliminates the mounting of a sensor switch on a variety of different carburetors used on different engines which would require many different carburetor mounting positions and/or locations. Placing all of the components of both the throttle position switch and the engine kill switch in a common housing also reduces the cost of this dual switch assembly and facilitates and simplifies mounting this duel switch assembly in the handle of a handheld tool since the switch housing can be configured so that it does not require any change in the handle mounting opening and typically the snap in mounting which would otherwise be used only for a conventional engine kill switch.
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.
This patent application claims the benefit of the earlier filed U.S. provisional patent application, Ser. No. 62/259,453, filed on Nov. 24, 2015, which is incorporated herein by reference in its entirety.
Filing Document | Filing Date | Country | Kind |
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PCT/US2016/063243 | 11/22/2016 | WO | 00 |
Number | Date | Country | |
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62259453 | Nov 2015 | US |