CA2109893C - Engine operational control unit - Google Patents

Abstract

An engine operational control unit for an internal combustion engine which protects an engine in the event of abnormal condition of the throttle mechanisms by discontinuing operation of the ignition or the ignition and fuel injection dependent upon engine speed. In this way, the engine is protected from overheating if operating at a high speed, and from wetting or fouling of the spark plugs if operating at a lower speed, if abnormal conditions prevail.

Description

2i09~9~
YAMAF12.334A PATENT v ENGINE OPER~1.TIONAL CONTROL UNIT
Background of the Invention This invention relates to an engine operational control unit and more particularly to a method and apparatus for S controlling an engine under abnormal coz~.ditiona.
A Common form of thxottle control for an internal combustion engine has a remotely positioned throttle control operated by the operator. This throttle control is connected by means of an interconnecting mechanism such as a bowden to wire actuator or the like to the actual thratt7,e of the engine far contro~.ling the engine speed. However, in some, instances, due to various forma of malfunction, the actual position of the throttle of the engine may not coincide in position with the operatox throttle ao~ttrol. When this 15 occurs, there is obviously a serious problem that requires protective action.
For example, in many types of vehicles, the throttle control and interconnecting mechanism is exposed to severe atmospheric conditions that can adversely affect the 2o operation. For example, in snowmobil.ee the throttle l~.nkage or bowc~en. wixa.: mechanism can easi~.y bpr..hme encrusted with ice or snow, and the throttle Qf the engine may become stuck in a position, that can cause problem9.
It has been proposed to provide a comparator that senses 25 the position of the throttle control and the throttle and wlliC:l1 w.Lll ehu4 off the eur~ixm by dieconl..i.uuily tkae a~upply e.C
current to the spark plugs for their f~.rang when this eond.~.tion occurs. Although this system has advantages, it can present certain difficulties.
30 For example, ifc the ignition is shut off whi3.e the engine is running, the engine will obviously not atop immediately. As a result, the engine will operate as a pump and wild. draw fuel into the engine~and di~ch~rge it to the atmosphere until the engine stops turning. This can give ripe to problems not only with emission, but also can give , difficulties on restarting.
For example, if fuel continues to be pumped through the engine when the ignition is shut off, the spark plugs will become wetted and foul, and restaxting with the same spark plu;~s~ can vexy well become impossible .
A solution to this.problem would be to also discontinue the supply of fuel to the engine when the ignition is shut off. However, this can be detrimental to the engine. For example, if the engine has been running at~a high speed, and a discrepancy vacate between the position of the throttle control and the position of the throttle, and the ignition and the fuel supply are shut off, then the engine will be deprived of any fuel while it continues to turn.w This will x5 mean that there is no cool3.ng of the engine duc to the vaporization of the, fuel, and damage to the engine can result.
It is, therefore, an object of this invention to provide an improved. eng~.ne control method and apparatus for protecting an engine in the event o~ abnormal conditions.
Tt is a further object of this invention to provide an impxQVed engine control apparatus and method for protecting an engine by discontinuing its operation under abnormal conditions,, but at the same t~.me eneuxi.ng that damage to the engine will not occur and reatart~.ng is facilitated.
Another diffioulty with the stopping of an engine under the abnormal condition of throttle position and throttle control position is that restarting of the engine can be difficult, as~aforenoted. In addition to the wetting of the spark plugs and possible fouling, the ambient conditions may be such that it would be diff~.ault or impossible to start tha engine after the defect has been remedied.
It is, therefore, a still further object of this invention to provide an engine control apparatus and method for protecting an engine in the event of an alanormal condition by discontinuing its operation but then rs-energizing the engine once the speed has fallen to a safe speed and maintaining the running at that new, safe, lower speed.
~ummarv of the Invention A fxx~st feature of this invention i.~x adapted to be embodied,in a method and apparatus ~ox engine control for an intesnal combustion engine having the charge forming system for supplying ~uel to the engine and an ignition system for to firing a charge in the engine for combustion and operation of the engine. A throttle i~ provided for controlling the speed of the engine, and a throttle position sensor is incorporated for providing a signal indicative of the throttle position.
In addition, an operator throttle control is operably 1s aor.~eatod to the throttle for manuz~~. positioning thereof . A
throttle Gaxltrol .position sensor is supplied ~or providing a signal indicative of the position of the throttle control.
In accordance with an apparatus for perfarming the control, a comparator means is provided that senses when a 20 discrepancy oacuxa between the position of the throttle control and the position of the throttle. If such an ahnoxma7 CQnr~irion is swnsed, means are provided for both disabling the ignition and discontinuing the supply of fuel by tlxe charge forming system.
25 ~A method for performing this invention Compares the position of the throttle control and the throttle, and indicates an abnormal condition a.f they are not cainG~.dent.
Upon the indication of an abnormal condition, both ignition and the supply of fuel to the charge former are discontinued.
3o Another feature of the invention is also adapted to be etnbddied in an engine control for an ~.nter, nab aomk~usr ion engine that is comprised of a chaxge forming system for supplyirre~ fuel to tha engine and an ignition system fear firing a charge in the engine for combustion and operation of 35 the engine. A throttle control far controlling the speed of the engine is provided, and a throttle position sensor i , 3 ' 2r09893 ' provides a signal ~.ndicative of the position of the throttle.
An operator throttle control is operably connected to the ' throttle for manually positioning the throttle. A throttle control position sensor senses the position of the throttle ' S control. Means are provided for also sensing the speed of f the engine.
In accordance with an apparatus fax performing this - invention, if the throttle control and throttle position ' sensors do not indicate that both the throttle control and throttle are in the same positions, and if the speed of the engine is greater thaw a predetermined speed, the ignition is interrupted. Once the speed of the engine falls below the predetermined speed, the ignition ie reinitiated so that the ' engine will continue to operate but at a lower speed.
Yn a method for perf~rming the invention, the throttle position and throttle control position are compared. if the COmpari8on Indicates that the positions are not the same, then it isdetermined if the speed is greater than a predetermined speed. If it is, the ignition is interrupted until the speed falls below the predetermined speed, and then ignition is reinitiated so that the engine will not operate at a speed greater than the predetermined speed until the condition is rectified.
Brie Dcoa~ipt~.on of the Drawing, 2~ Figure 1 is a side elevational view of a. snowmobile constructed in accordance with an embodiment of Lhe invention.
Figure 2 is a partially sohematia cross-sectional view taken through a single cylinder of the engine and shows the interre~.ationship with the throttle control and other controls for the system.
Figure 3 is a block diagram of the control routine.
Figure 4 i~ a graphical triew showing the eonditiong ~f the various position detectors, engine speed, ignition, fuel infection and alarm lamps to understand ctzG operation of the . control routine, _~_ ' ' ,2iU9893 Detailed Description of the Preferred Embodirnene Referring now in detail to the drawings and initially to Figure 1, a snowmobile constructed and operated in accordance ' with an embodiment of the invention is identified generally by the reference numeral 11. The invention is described in oonjtt2zctiox~ with a snowmobile because this is a typical environment in which the invention may find the utility. As will become apparent, the inventir~n deals pra.marily with the controls for the powering internal Combustion engine of the snowmobile 11 and snowmobiles provide the type of environment where the invention, which protects against certain types of malfunctions in the throttle control meahaz~iem. are useful.
zt will be obvious to those ski~,led in the art that the invention can be employed with other applications for internal combustion cxiginee .
The snowmobile ~.1 includes a body 12 that is suspended upon a pair of steering skis 13 at the front and a drive belt 1~ at the rear. The skis 13 and drive belt 14 suspend the body 13 through any known type of suspension systems.
A handle bar assembly 15 is supported on the body 12 forwardly of a rider s seat 16 for controlling the steering of the aki.s 13 in a wel7~knawn manner. Other controls for the snowmobile 11 are also carried by the handle bar assembly 15, as will beGOme apparent.
.An internal Combustion engine, indicated generally by the reference numeral 17 and shown in most detail ~.n Figure ~, is mounted in the body 12 and drives the drive belt 14 through a suitable transmission which includes a centrifugal clutch (not shown).
Referring new in detail. to Figure 2, the engine 17 is depicted partially in schematic form and as a cross-section through a single cylinder. Since the internal details of the engine 17 axe not necessary to understand the oanstruction and operation of the invention, they will be described only summarily. Where a detailed description ~.s omitted, it quay be considered to be conventional.
_5_ 2~~.09~93 The engine 17 includes a cylinder block 18 having one or ' more cylinder bores in which pistons 19 are supported for r reciprocation. The pistans 19 and cylinder bores as well as ' an attached cylinder head define a combustian chamber 21.
The pistons 19 are connected by means of connecting rods 22 to the throws a3 of a Crankshaft, indicated generally by the reference numeral 24, and supported within a crankcase 25 in a known manner. In the illustr~xted embodiment,, the engine ~.7 operates on a two-strake crankcase compression principle, x0 although it should be readily apparent to those skilled in the art that the invention can be employed with engines operating on other principles.
As a two-stroke engine, the crankcase chambers associated with each o~ the pistons 19 are sealed-from each x5 other and a fuel/air charge is delivered to the arazlkcase ' Chambers through an,inductian system that includes an air cleaner 26 which draws atmospheric ai.r from within the body 12 and delivers it to an induction manifold 27. A flow controlling throttle valve 28 i.s provided in the induction 20 manifold 27 and the throttle valve 28 is controlled by a throttle letter 29 mounted on one side of the handle bar assembly 15. A bnwden wire actuator 31 ox other motion transmitting mechanism interconnects the throttle control lever 29,writh the throttle valve 2a.
25 .A charge forming system is provided for supplying a ~ue1/air charge to the intake maniEo~.d z7 and in the illustrated embodiment, this eharge-forming embodiment includes an electrically operated fuel injector 32 having a discharge noxxle 33 that sprays fuel into the intake manifold 30 27 downstream of the throttle valves 28. Although manifold injection zs disclosed, it is rra ba understood that the invention may also be employed in conjunction with direct cylizidst injact~,on or other types of ohrzrge-form~.ng systems such as carburetors or the like.
35 The charge formed in the ~.nduct~,on system is delivewed to the crankcase chambers through the intake manifold 27 and 2.09893 reed-type check valves (not shown) are provided at the discharge point so as to preclude reverse flow when the charge is being compressed by the downward movement of the pistons 19, as is well-known in this art.
The charge compressed in the crankcase chambers is then transferred to the rnmbuetinn chambers 27. by scavenging passages (not shown?. This charge ie then fired by a spark plug 34 mounted in the cylinder head of the engine and having its spark gap extending into the combustion chamber 21, An iD ignition coil 35 connected to the spark plug 34 fox its firing and the ignition coil 35 is controlled, in a manner which will be described.
When the charge in the combustion chamber 2~. is fired by the spark plug 34, the pistans 19 will be driven~downwardly 1S and eventually will span 2~chaust ports 36 which communicate with an exhaust system (not shown) for the discharge of the exhause gases to the atmosphere.
The fuel injector 32 arid ignition system including the ignition coil 35 are contxalled by an engine operational 20 control unit, indicated generally by the reference numara~. 37 and which received certain signals from the engine 17 and amb~.ent Conditions, if desired, so as to provide the appropriate timing and duration of fuel injection by the 3njcctor 32 and timing of firing of the spark plug 34. Since 25 the basic eng~.ne control may be of any known type, further details of Sts construction are npt believed to be necessary to understand the construction and operation of the invention.
The construction thus fax described may be considered to 3D be conventional and, for that reason and as previously noted, full details of the construction are not believed to be necessary to understand the construction and operation of the invention. The invention deals pximarily with a system fdr protecting the engine 17 in the event of an abnormal 35 condition, this being nonconcurrence of lace position of the throttle control 29 and the thrott~.e valve 28. Such _7_ 2~.09~'~3 ,,.-., condition can occur due tp encrustation o~ the wine actuator 31 or other throttle actuating mechanism. As previously noted, this can present certain difficulties and the ' invention deals with a system for protecting against such problem.
The engine protection system iviG~ ude~e s throt tle position detector 38 that outputs a signal to the engine operat~.anal control unit 37 which is ~.nd~.cative o~ the po8ition of the throttle valve 28. Tn addition, a throttle lever control position sensor 39 is mounted on the handle bar assembly 15 and cooperates with the thr4ttle control levex 29 eo a8 to output a signal to the engine operational control unit 37 indicative of throttle control lever position.
There is Further provided an engine speed sensor 41 of any known typo which cooperates with the aranJcshaft 24 for providing output pulses for each revolution of the crankshaft 2~ so as to provide data by which the engine opera.t~.anal control unit'37 may determine engine speed N. It should be noted that some or all of the sensors 38, 39 and ~1 may also be employed in the basis engine control.
The system further includeB a warning or alarm lamp 42 that is mounted in proximity to the handle bar assembly 15 so that the.operator will be warned of certain malfunctions in accordance with the control routine. to be descxibed.
~ As has been previously noted, the basic control for the ignition coil 35 anti fuel injector 32 may be of tray known type and the normal control operation will, therefore, not be described. Only the system for determining abnormal engine conditions and the protective action associated therewith wil3. be described by reference to figures 3 and 4.
Basically, the control routine functions so as to Compare the relative positions of the throttle control lever 29 and throttlE valve 2B, arad if their positions do not coincide, then it is determined if the engine~speed N is greater than a predetermined relatively high engi.rae speed Eli. ~f the speed is greater than this speEd, then the ignition is shut Wg_ aff by discontinuing the ignition signal Erom the operational .
aontxol unit 37 to the ignition coil 35. xf the engine is ~, operating at a higher speed than the speed N1, it is not desirable to disdont~.riue the fuel injection because th~.s will possibly cause overheating damage to the engine.
.Also, if the ex~gi,tle speed N is greater than or equal to a predetermined lower speed N2, when fuel shut off i~s safe then the Euel in~ect~.on amount is also discontinued by having the engine operational control unit 37 discontinue aetuation 7.0 of the fuel injector 32.
The specific control routine will now be described by particular reference to Figure 3, which is a block diagram of the control routine and Figure ~ which is a time history showing the relation of throttle control paeition-, thxottle valve position, engine speedy ignition command, fuel injection command and alarm lamp condition. The program begins and moves to the step 81 to determine if the throttle control lever 29 is in its closed or idle position. In this control routine, abnormal conditions are determined if either the throttle control 29 ie in its idle position and the throttle valve 2B is not in its idle positi.an, or if the throttle control lever 29 is in an open pe~si i:i can an$ t~.he throttle valve 28 is retaixxed in an idle position.
IE at the sl.ep S1 it is determined that the throttle control lever 29 is not in its idle or closed position, the program then moves to the step S2 to determine if the throttle valve 28 is in its idle or closed position. This is determined by the output from the throttle position sensor 38. If the throttle valve 28 is determined at the step S2 to g0 be not in its idle condition, then the program moves to the step 83 which determines normal engine aperatian an~3 the program repeats back to the step S1.
~hia condition occurs as shown at the lofthand Aide of the time history of Figure 4 wherein both the thxottle control lever and the throttle valve axe not in theLr 5.dle positions.
_g_ If, however, at the step S2, it is determined that the throttle valve 28 is not in its idle condition, then the program moves to the step S4 so as to determine the existence of an abnormal condition. The program then moves to the step ' SS so as to turn on the alarm lamp ~2 and warn the operator.
The program then returns to the step Sl.
In the condition as thus far described, the throttle lcvcr has been determined initially to be in an open positive but the throttle valve 28 has been stuck in a closed or idle position. The operator need be warned in this situation but no protective action is required under this particular running condition.
When the program returns to the step 81, and it is determined either then ox initially that the thrott7.e control iS lever 29 i.s per,f.actly closed, then the program moves to the step S6 to read the position of the throttle valve 28 again by the throttle position sensor 38. If the throttle valve 28 ~.s perfectly closed, then the program moves to the step S7 so as to indicate a normal condition. And this control routine will be de~saribed later.
If, however, at the step S6 it is determined that the throttle valve 28 is not perfectly closed, then the program moves to~the step Se to determine if the time when the throttle valv~ has not been perfectly closed but the throttl a control level is closed exceeds a predetermined time period T1 which time period Iaas a duration of about o . 5 aseaflnds .
This time period is chosen so as to avoid the effects of noise a.n the system and also to ensure that the components have had an opportunity to stabilize in the condition.
xt the time period T1 has not been exceeded at the step S8, the program repeats back to the step S6.
If, however, the time period T~ has been exceeded as shown in Figure ~, then the program moves to the step S9 ao as to determine that there is an abnormal condition and that protective action may be required.
-2p-The program then moves to the step S10 ao as to compare ' the actual engine speed N with the preset relatively higher engine speed N1. As may be seen in Figure 4, the speed N1 is a speed high enough that the centrifugal clutch of the S snowmobile 1~. will be engaged and the drive belt 14 would be driven_ This may be a dangerous condition if the eperator is calling for idle operation and hence, if the speed is equal to or greater than the speed N1, the pzogram moves to the step S10 so as to discontinue the ignition. As noted, this to is done by having the operational control unit 37 discontinue the supply of power to the ignition coil 35.
The program then moves to the step S12 so as to turn on the warning light 42 and then repeats back to the step 51.0 to determine if the engine speed has ~allen to a speed below the 15 speed N~. Tf it has not, the program continues to repeat so as to discontinue the firing of the spark plugs 34. However, it should be noted. at this time that no fuel in~ecti.on termination occurs because of the high speed at which the engine 17 ie running.
20 Once the engine speed fallo below or equal to the engine speed Nl, then the program moves to the step 813 to determine if the engine speed N is equal to or greater than the lower engine speed N~. The speed Nz is set as a speed slightly above i$1e speed but a speed below that at which the 25 centrifugal clutch that drives the drive belt 1.4 would be engaged. This speed is chosen so as to ensure that the engine will continue running but not at such a high rate of speed that there will be any danger. Because of the environment at which the snowmobile exists, it is not 30 desirable to completely shut down the engine merely because the throttle valve poa~.ti.on does not coincide with the throttle control position so long as the speed is kept relatively low.
If, at the step 513, it is determined that the speed of 3~ the engine N is greater than or equal to the speed Nx, this aanditian aacurring during the time periods P1 and Pz in -i Figure 4, then the program initiates trie step si4 wherein both fuel injection and ~.gnition are discontinued. The v program then moves to the step S15 so as to maintain the warning light 42 in its ON condition. The program then repeats to the step 813.
Assuming at the return to the step 813, the engine speed has fallen .to a speed equal to or less than the speed NZ, the program then moves to the step S16 so as to resume the firing of the spark plugs 34 and fuel inj ectian by the fuel in j actor 32 while still retaining the warning lamp 42 on. The program then repeats back to the step S1. As may be seen from figure 4, this operation assuming the malfunction condition maintains will ensure that the engine is running at a speed approximately equal to the speed Na and will not be Z5 completely stopped.
Returning now to the step S7 when it is determined that the conditions may be determined to be normal., the pxogxam then maven to the step S18 to determine if this normal condition occurs for a time period at least equal to a time ~ period TZ. This time period may also be appraximatel,y o.5 seconds and appears at the end of the P3 time period in Figure 4. ~f the time period of normalcy exceeds the time period Tz, then it is determined that the abnormal condition has ceased to exist and the program mov'eo to the step 819 to turn off the warning lamp 42 and the program then returns to the step S1.
It should be understood that the described control routine is designed primarily for conditions where the throttle cQntxol lever 29 is in the idle position and the throttle valve 28 is not in the idle position or when the throttle control lever 2~ is in the off idle or span condition and the throttle valve 28 is stuck in the idle condition. Of course, it ohould ba readily apparent to those skilled in the art how the control routine may also be practiced under other conditions when the positioia c~f the throttle control lever 29 and throttle valve 28 do not . 2,109893 v coincide. Also, it is to be understood that the described v construction is that of a preferred embodiment of the invention and various other changes and modifications may be made without departing from the spirit and scope of the xrlvent~.o~., a~ defined by the appended claims.
°~.3- s.

Claims (36)

1. An engine control for an internal combustion engine comprising a charge forming system for supplying fuel to said engine, an ignition system for firing a charge in said engine for combustion and operation of said engine, a throttle for controlling the speed of said engine, a throttle position sensor for sensing the position of said throttle, an operator throttle control operably connected to said throttle for manual positioning thereof, a throttle control position sensor for sensing the position of said throttle control, comparator means for comparing the outputs of said throttle position sensor and said throttle: control position sensor and providing an abnormal condition signal when said sensors are not coincident, means for discontinuing the firing of the ignition system and the supply of fuel from the charge forming system in response to the sensing of the abnormal condition, and means for sensing the speed of the engine, the discontinuance of the firing of the: ignition system and the supply of fuel from the charge forming system being determined depending upon the speed of the engine.

2. An engine control for an internal combustion engine at set forth in claim 1, wherein the ignition of the engine is discontinued when the speed of the engine is greater than a first predetermined speed.

3. An engine control for an internal combustion engine as set forth in claim 2, wherein the discontinuing of the supply of fuel from the charge forming system is initiated at a second predetermined speed.

4. An engine control for an internal combustion engine as set forth in claim 3, wherein the second predetermined speed is lower than the first predetermined speed.

5. An engine control for an internal combustion engine as set forth in claim 4, wherein the firing of the ignition system and the supply of fuel from the charge forming system is reinitiated when the speed of the engine falls below the second predetermined speed and is again discontinued when the speed exceeds the second predetermined speed.

6. An engine control for an internal combustion engine as set forth in claim 1, wherein the comparator means compares the position of the throttle control position sensor and the throttle position sensor when the throttle control position sensor indicates that the throttle control is in an idle condition.

7. An engine control for an internal combustion engine as set forth in claim 6, further including means for sensing the speed of the engine and wherein the discontinuance of the firing of the ignition system and the supply of fuel from the charge forming system is determined depending upon the speed of the engine.

8. An engine control for an internal combustion engine as set forth in claim 7, wherein the ignition of the engine is discontinued when the speed of the engine is greater than a first predetermined speed.

9. An engine control for an internal combustion engine as set forth in claim 8, wherein the discontinuing of the supply of fuel from the charge forming system is initiated at a second predetermined speed.

10. An engine control for an internal combustion engine as set forth in claim 9, wherein the second predetermined speed is lower than the first predetermined speed.

11. An engine control for an internal combustion engine as set forth in claim 10, wherein the firing of the ignition system and the supply of fuel from the charge forming system is reinitiated when the speed of the engine falls below the second predetermined speed and is again discontinued when the speed exceeds the second predetermined speed.

12. An engine control for an internal combustion engine as set forth in claim 11, further including means for providing a warning signal when the throttle control position sensor indicates that the throttle control is not in its idle position and the throttle position sensor indicates that the throttle position is in its idle condition.

13. An engine control for an internal combustion engine as set forth in claim 6, further including means for providing a warning signal when the throttle control position sensor indicates that the throttle control is not in its idle position and the throttle position sensor indicates that the throttle position is in its idle condition.

14. An engine control for an internal combustion engine comprising a charge forming system for supplying a fuel charge to the engine, an ignition system for firing said fuel charge in the engine for combustion and operation of said engine, a throttle for controlling the speed of said engine, a throttle position sensor for sensing the position of said throttle, an operator throttle control operably connected to said throttle for manual positioning thereof, a throttle control position sensor for sensing the position of said operator throttle control, means for sensing the speed of said engine, and comparator means for sensing when the position of said operator throttle control and said throttle are not coincident and discontinuing the operation of said ignition system if the engine speed sensor indicates the engine speed is above a predetermined speed until the speed of the engine falls below a predetermined speed, and means for discontinuing the supply of fuel to the engine from the charge forming system while the operation of said ignition system is discontinued.

15. An engine control for an internal combustion engine as set forth in claim 14, further including the reinitiation of the operation of the ignition system when the engine speed falls below the predetermined speed.

16. An engine control for an internal combustion engine as set forth in claim 14, wherein the supply of fuel to the engine from the charge forming system and the firing of the ignition system are reinitiated when the engine speed falls below the predetermined speed.

17. An engine control for an internal combustion engine as set forth in claim 16, further including means for discontinuing the firing of the ignition system only when the engine speed is above a second predetermined engine speed higher than the first predetermined engine speed.

18 18. An engine control method for internal combustion engine comprising a charge forming system for supplying fuel to said engine, an ignition system for firing a charge in said engine for combustion and operation of said engine, a throttle for controlling the speed of said engine, an operator throttle control operably connected to said throttle for manual position thereof, said method comprising the steps of determining the position of said throttle, determining the position of said throttle control, comparing the positions of said throttle and said throttle control and providing an abnormal condition signal when said sensors are not coincident, discontinuing the firing of the ignition system and the supply of fuel from the charge forming system in response to the signal condition, and sensing the speed of the engine and wherein the discontinuance of the firing of the ignition system and the supply of fuel from the charge forming system is determined depending upon the speed of the engine.

19. An engine control method for an internal combustion engine as set forth in claim 18, wherein the ignition of the engine is discontinued when the speed of the engine is greater than a first predetermined speed.

20. An engine control method for an internal combustion engine as set forth in claim 19, wherein the discontinuing of the supply of fuel from the charge forming system is initiated at a second predetermined speed.

21. An engine control method for an internal combustion engine as set forth in claim 20, wherein the second predetermined speed is lower than the first predetermined speed.

22. An engine control method for an internal combustion engine as set forth in claim 21, wherein the firing of the ignition system and the supply of fuel from the charge forming system is reinitiated when the speed of the engine falls below the second predetermined speed and is again discontinued when the speed exceeds the second predetermined speed.

23. An engine control method for an internal combustion engine as set forth in claim 18, wherein the position of the throttle control and of the throttle indicates that the throttle control is in an idle condition.

24. An engine control method for an internal combustion engine as set forth in claim 21, further including sensing the speed of the engine and discontinuing the firing of the ignition system and the supply of fuel from the charge forming system is dependent upon the speed of the engine.

25. An engine control method for an internal combustion engine as set forth in claim 24, wherein the ignition of the engine is discontinued when the speed of the engine is greater than a first predetermined speed.

26. An engine control method for an internal combustion engine as set forth in claim 25, wherein the discontinuing of the supply of fuel from the charge forming system is initiated at a second predetermined speed.

27. An engine control method for an internal combustion engine as set forth in claim 26, wherein the second predetermined speed is lower than the first predetermined speed.

28. An engine control method for an internal combustion engine as set forth in claim 27, wherein the firing of the ignition system and the supply of fuel from the charge forming system is reinitiated when the speed of the engine falls below the second predetermined speed and is again discontinued when the speed exceeds the second predetermined speed.

29. An engine control method for an internal combustion engine as set forth in claim 28, further including the step of providing a warning signal when the throttle control is not in its idle position and the throttle is in its idle condition.

30. An engine control method for an internal combustion engine as set forth in claim 21, further including the step of providing a warning signal when the throttle control is not in its idle position and the throttle is in its idle condition.

31. An engine control method for an internal combustion engine comprising a charge forming system for supplying a fuel charge to the engine, an ignition system for firing said fuel charge in the engine for combustion and operation of said engine, a throttle for controlling the speed of said engine, an operator throttle control operably connected to said throttle for manual positioning thereof, said method comprising the steps of sensing the position of said throttle, sensing the position of said operator throttle control, sensing the speed of said engine, and if the position of said operator throttle control and said throttle are not coincident discontinuing the operation of said ignition system if the engine speed is above a predetermined speed until the speed of the engine falls below a predetermined speed, and discontinuing the supply of fuel to the engine from the charge forming system while the operation of the ignition system is discontinued.

32. An engine control method for an internal combustion engine as set forth in claim 31, further including reinitiation of the operation of the ignition system when the engine speed falls below the predetermined speed.

33. An engine control method for an internal combustion engine as set forth in claim 31, wherein the supply of fuel to the engine from the charge forming system and the firing of the ignition system are reinitiated when the engine speed falls below the predetermined speed.

34. An engine control method for an internal combustion engine as set forth in claim 33, further including discontinuing the firing of the ignition system only when the engine speed is above a second predetermined engine speed higher than the predetermined engine speed.

35. An engine control for an internal combustion engine comprising an ignition system for firing a charge in the engine for combustion and operation of said engine, a throttle for controlling the speed of said engine, a throttle position sensor for sensing the position of said throttle, an operator throttle control operably connected to said throttle for manual positioning thereof, a throttle control position sensor for sensing the position of said operator throttle control, means for sensing the speed of said engine, and comparator means for sensing when the position of said operator throttle control and said throttle are not coincident and discontinuing the operation of said ignition system if the engine speed sensor indicates the engine speed is above a predetermined speed until the speed of the engine falls below a predetermined speed, wherein the comparator means compares the operator throttle control position and the throttle position when the throttle control position sensor indicates that the operator throttle control is in an idle condition.

36. An engine control method for an internal combustion engine comprising an ignition system for firing a charge in the engine for combustion and operation of said engine, a throttle for controlling the speed of said engine, an operator throttle control operably connected to said throttle for manual positioning thereof, said method comprising the steps of sensing the position of said throttle, sensing the position of said operator throttle control, sensing the speed of said engine, and if the throttle control position sensor indicates that the operator throttle control is in an idle condition and the position of said operator throttle control and said throttle are not coincident discontinuing the operation of said ignition system if the engine speed is above a predetermined speed until the speed of the engine falls below a predetermined speed.