US3020777A

US3020777A - Two-cycle engine idling speed limiter

Info

Publication number: US3020777A
Authority: US
Publication date: 1962-02-13
Anticipated expiration: 1979-02-13

Description

Feb. 13, 1962 w. B. BURKETT TWO-CYCLE ENGINE IDLING SPEED LIMITER 2 SheetsSheet 1 Filed Aug. 19, 1959 r n R." w M M 0 r h w.

Feb. 13, 1962 w. B. BURKETT 3,020,777

TWO-CYCLE ENGINE IDLING SPEED LIMITER Filed Aug. 19, 1959 2 Sheets-Sheet 2 INVENTOR.

Wu. FORD B. Bum r hzhzza z lrroausra United States atet 3,020,777 Patented Feb. 13, 1962 3,020,777 TWO-CYCLE ENGINE IDLING SPEED LllVlITER Wilford B. Burkett, Minneapolis, Minn., assignor to Me- Culloch Corporation, Marine Products Division, Minneapolis, Minn., a corporation of Minnesota Filed Aug. 19, 1959, Ser. No. 834,740 7 Claims. (Cl. 74-472) This invention relates to a speed control for limiting the no-load idling speed of a two-cycle internal combustion engine.

- The speed of two-cycle internal combustion engines is usually controlled by retarding and advancing the ignition and controlling the fuel mixture intake. When used in outboard motors these engines are connected to the propeller by clutches and manually shiftable gears such as described by D. A. Armstrong et al., Patent No. 2,653,- 277, issued December 22, 1953, the operation of which is described beginning at line 17 of column 7. It may be noted that the motor has a neutral position wherein the two-cycle engine is effectively disconnected from the propeller and thus in a no-load condition.

In two cycle engines, particularly the larger ngines, there is a tendency for the engine during no-load conditions to maintain increased engine speeds at a dangerous and harmful level regardless of the spark and fuel mixture adjustments. This speed runaway is believed caused by back breathing through the exhaust ports providing insufiicient scavenging of diluted fuel mixture in the combustion chamber. Every several cycles a combustion charge is accumulated to keep the engine running at increased speeds.

Previously the increased speed has been prevented by sensing the vacuum in the intake manifold and using high manifold vacuum as a criterion for shorting the ignition to ground and thus preventing the excessive speed. It has been noted that the pressure variation in the intake manifold was slight, the total pressures being measured in inches of water column. This absolute pressure variation is also dependent on the carburetor adjustments and therefore subject to variations with respect to true engine s eed.

This invention provides two-cycle engine idling speed controls in which the control is stably related to true engine speeds regardless of engine adjustments. Additionally control means are provided in which the engine speed is limited to the desired idling speed even when the actual spark or fuel mixture adjustment are adjusted as to provide an engine speed greater than the desired speed. According to this invention a pressure sensitive switch is operatively connected to the coolant system which provides a high pressure proportionately related to engine speed for use as a criterion in making the ignition system ineffective to produce a spark. Additionally an interlock switch is provided on the gear shift or clutch lever making the pressure sensitive switch electrically operative only during periods of engine no-load conditions.

These and other more detailed and specific objects will be disclosed in the course of the following specification, reference being had to the accompanying drawings, in which:

FIG. 1 is a vertical axial sectional view through an outboard motor embodying the invention.

FIG. 2 is a sectional view of an engine block installed pressure responsive switch together with a schematic diagram of the idling speed controls for use in a battery operated two-cycle engine.

FIG. 2A is a modification of the FIG. 2 circuit.

FIG. 3 is a schematic diagram of an idling speed control for use with a magneto operated two-cycle engine.

FIG. 4 is a schematic diagram of an idling speed control for use with an outboard motor having magneto operated individual ignition systems for each cylinder.

With more particular reference now to the drawing like numbers denote like parts and structural features in the views and various schematic diagrams. In FIG. 1 there is shown an outboard motor having a power head 10 with a two cylinder two-cycle internal combustion engine 12 therein. The engine 12 has a vertical drive shaft 14 gearingly driving the usual propeller 16. On the forward side of the vertical housing 18 there is a water or coolant intake 20 coupled to water or coolant pump 22 driven by the shaft 14 for pumping Water from a boat supporting body of water (not shown) through a tube 23 to the engine block 24 for cooling same. The water coolant leaves the block 24 through restricted outlet tube 25 into the exhaust system of the motor. Since pump 22 is directly driven by the shaft 14 on the engine side of the clutch generally designated by numeral 26, the water or coolant pressure in block 24 is proportionately related to the engine r.p.m. or speed and provides up to 8-10 p.s.i. water pressures.

In power head 10 an ignition system 28, of either the battery or magneto type, provides timed electric spark to spark

plugs

30 and 31 for igniting the fuel mixture in the engine cylinders. Also the usual gear shift lever 32 provides control over the gear shifting structure of Armstrong et al., supra, and has a forward, neutral and reverse positions respectively indicated by

dotted lines

32, 32 and 32.

The improvements provided by this ignition include a cam element 34 attached to gear shift 32 and disposed with relation to spring loaded switch 36 to actuate same when the gear shift is in the neutral position 32 and permitting the switch to return to its spring urged normal position as will be more fully described. It may therefore be seen that switch 36 will be actuated when the gear shift 32 is in a neutral position.

Switch 36 is electrically connected to a pressure responsive switch 38 in an ignition system controlling conjunctive circuit relation. That is, both

switches

36 and 38 are actuated to effect the desired control over ignition system 28. This is more easily understood with reference to FIG. 2 wherein switch 38 comprises a threaded nipple 40 screwed into an engine block portion 24 for admitting coolant therethrough to exert pressure against circular flexible diaphragm 42 flexing it to close the normally open contacts 44 making an electrical circuit at a pressure determined by spring 42*. One of the contacts 44 is electrically grounded to the engine block 24 and thus connected to the grounded side of battery 46. The other contact is connected to insulated terminal 44 which in turn is connected to one side of gear shift operated normally open switch 36, the other side of which is connected to the battery 46 through a small current limiting resistance. From this it is seen that both

switches

36 and 38 must close conjunctively to ground the circuit between the battery 46 and the coil 54 to make the ignition system 28 ineffective.

A timing cam 48 opens and closes the breaker points 50 in synchronism with the drive shaft 14 rotation to,

provide timed spark. The ignition primary circuit connects the battery 46 through closed points 50 and coil 54. When points 50 open the capacitor 52 charges rapidly through the primary winding of the ignition transformer or coil 54 to provide the spark producing electric current in the coil secondary winding to plug 30 and 31 through the usual ignition distributor 55.

The switch 38 actuates at a pressure slightly above the desired highest idling engine speed and it being in conjunctive electrical ignition control circuit relation with the gear shift actuated switch 36 to obviate the two-cycle engine idling runaway condition as well as providing an absolute maximum idling speed.

Alternately normally closed parallel connected pressure and gear shift responsive ignition conjunctively controlling switches may be series connected between the battery 46 and the coil 54. As shown in FIG. 2A the normally closed parallel connected switches 36C and 38C connect the battery 46 to the ignition primary circuit portion including coil 54 primary winding and points 50 to ground as indicated by the FIG. 2A arrows. To make the ignition system ineffective by breaking the primary ignition circuit both switches 36C and 38C are simultaneously opened; the switch 36C being opened by moving the gear shift to neutral and the switch 38C being opened by the water coolant pressure indicating a speed exceeding the predetermined maximum engine idling speed.

It is understood that where individual battery operated ignition systems are provided that the just described embodiments may be utilized by connecting the ignition coils of each system to switch 36 as coil 54 is connected. Also the selection of the ground point in the primary ignition circuit is arbitrary and it may be made at any convenient circuit junction.

FIGS. 3 and 4 illustrate two embodiments of this invention for use with two-cycle engines having a separate ignition system for each cylinder and where the ignition is short circuited to make it ineffective. In FIG. 3 there is a magneto generator having separate spark

current generating circuits

56 and 57 each including a magneto spark coil 60 and ignition capacitor 62 with the coil secondaries being connected to the

spark plugs

30 and 31. The breaker points 58 are actuated by engine 12 to provide synchronized ignition to the plugs 3031 in the usual manner.

To make ignition systems ineffective by shorting a normally open switch or series connected normally open switches are connected in parallel circuit relation to each primary winding 60 In the FIG. 3 illustration two separate series switch elements in conjunctive controlling relation are required to make both ignition systems ineffective therefore switches 36 and 38' are constructed with normally open double pole single

throw switch elements

36, 36 38 and 38 and connected across primaries 60 as shown in FIG. 3. When the gear shift 32 is in neutral, closing switch 36', and the engine speed has created sufiicient coolant pressure to close switch 38' it is seen that the primaries are short circuited thereby providing no ignition current to plugs 30 and 31. Alternately only one ignition system need be short circuited with equally effective, results to prevent idling speed runaway and to provide an absolute no-load engine speed greater than the speed indicated by the coolant pressure.

FIG. 4 illustrates this invention applied to magneto operated individual cylinder ignition systems wherein shorting the ignition coil primary through the non-firing points makes the ignition system ineffective. This latter embodiment is preferred for ignition systems wherein the timing cam is designed such that the non-firing points are closed at the time the firing points open. Magneto coils 66 and 67 provide spark current in the usual manner respectively when the timed breaker points 64 and 65 break. The timing arrangement is such that points 64 are closed when points 65 are breaking to provide the spark to plug 31, and vice versa. Switches 36" and 38", actuated as heretofore described for the

switches

36 and 38, are series connected between the coil side of the points 64 and 65 for limiting the engine idling speed. When the switches are closed and either of the points break to provide spark the respective ignition system is grounded through the non-firing or other points, thereby providing grounding of separate ignition systems through a pair of singlepole single through throw switches.

It is understood that suitable modification may be made in the structure as disclosed, provided such modifications come within the spirit and scope of the appended claims. Having now therefore fully illustrated and described my invention, what I claim to be new and desire to protect by Letters Patent is:

1. In an outboard motor having a two-cycle engine, a gear shift means having a neutral position, an ignition system, an engine cooling system including a coolant pump operatively connected to the engine for creating a coolant pressure related to engine speed, a pressure responsive switch operatively connected to said system for actuating at a predetermined coolant pressure, switch means operatively connected to the shift means for actuation when said gear shift means is in a neutral position, said pressure responsive switch and said switch means being electrically connected in conjunctive controlling circuit relation to the ignition system for making the ignition ineffective when said pressure responsive switch and said switch means have been actuated.

2. For limiting the no-load two-cycle engine idling speed of an outboard motor, a battery, a battery operated ignition system including a primary circuit, the improvement comprising a gear shift controlled normally closed switch indicating a neutral gear shift position when open, means in the engine providing a fluid pressure related to engine speed, a pressure sensitive switch operatively connected to said pressure means for opening at a predetermined pressure, and the said switches being connected in a parallel circuit which is series connected in the primary circuit for making the ignition ineffective when both switches have opened.

3. In an outboard motor having a two-cycle engine, a gear shift having a neutral position wherein the engine is operating under a no-load condition, an engine cooling system having coolant pressures related to enginespeed, an electrical ignition system having a primary circuit including an ignition coil with a primary winding, and normally open switch means connected across the primary for short circuiting the primary winding and being responsive to a coolant system pressure indicative of an engine speed greater than a predetermined engine idling speed and which is concurrent with the gear shift being in a neutral position.

4. In an outboard motor having a two-cycle engine, a gear shift having a neutral position wherein the engine is operating under a no-load condition, an electrical ignition system having a primary circuit including an ignition coil primary winding, means in the engine providing a fluid pressure related to engine speed, a pressure responsive switch operatively connected to said means for closing at a predetermined pressure, a normally opened switch operatively connected to the gear shift to close when the gear shift is in the neutral position, and the said switches being connected in series across the primary winding for making the ignition system ineffective under no-load condition at a predetermined engine speed.

5. In an outboard motor having a two-cycle engine, a gear shift having a neutral position wherein the engine is operating under a no-load condition, an engine cooling system having coolant pressures related to engine speed, a timing cam, an electrical ignition system having two sets of breaker points each having one ungrounded contact and being operatively associated with the timing cam such that one set is closed when the other set is opening for firing, a normally open pressure responsive switch operatively connected to the coolant system and responsive to a predetermined pressure therein for closing, a normally open switch operatively connected to the gear shift for closing when the shift is in neutral, and the switches being series connected between the ungrounded contacts.

6. For limiting the no-load speed of a two-cycle engine, an engine coolant system developing pressures related to engine speed, a gear shift having a neutral position wherein the engine is in a no-load condition, an electrical ignition system having a primary circuit with a portion including an ignition coil primary, normally open switch means electrically connected in parallel with said primary circuit portion and being operatively connected to the coolant system and to the gear shift, and the means being responsive to coolant system pressures exceeding a predetermined pressure and to the gear shift being in neutral for closing to make the ignition system ineffective by shorting said circuit portion.

7. For limiting the no-load speed of a tWo-cycle engine, an engine coolant system developing pressures related to engine speed, a gear shift having a netural position wherein the engine is in a no-load condition, an electrical ignition system having a primary circuit, normally closed switch means electrically connected in series with the primary ignition circuit and being operatively References Cited in the file of this patent UNITED STATES PATENTS 1,771,866 Stevenson et a1 July 29, 1930 2,034,233 Hasselbaum Mar. 17, 1936 2,131,264 Benjamin Sept. 27, 1938 2,762,235 Olson et a1. Sept. 11, 1956