US2621641A - Vacuum ignition mechanism - Google Patents

Description

Dec. 16, 1952 M. STERNER VACUUM IGNITION MEcHANIsM Filed Oct. 2, 1950 Nik Melvin Shrine)- INVENTOR.

HTTap/VEY d Patented Dec. 16, 1952 VACUUM IGNITION MECHAN ISM Melvin Sterner, Royal Oak, Mich., assigner to George M. Holley and Earl Holley Application October 2, 1950, Serial No. 187,915V

s Claims; (c1. 12s-,117)

The object of this invention is to control the spark advance of an Vautomobile by means of both inlet manifold vacuum'fand theva'cuum created by the throat of the venturi of the plaintube carburetor in general use. -Heretofore there have been two rival and partially successful commercial solutions, namely: V y

(1) To meter the two vacuums through two short restricted passages or jets so as to obtain a practical compromise between them so that as the engine throttle isopened and closed the two vacuums controlled thereby act against a diaphragm'to rotate a circuit breaker plate against the restraining action of a loose-spring and an initially tight tension spring to give correct spark advance.

(2)` Toiprovide a spring loaded check valve, normally seated, so as to'prevent the low manifold vacuum which exists at wide open throttle from diluting the Venturi vacuum.

The objections to both systems are as follows:

(A) It is difficult with (1) to obtain sufficient vacuum especially at wide open throttle position to reliably operate the spark mechanism in view of the presence of dust and the undesirable effect of over lubrication on the life of the tungsten points.

Again, when closing the throttle from its wide open position to its road load position after attaining the desired road speed (direct gear) by accelerating the engine by opening the throttle; there was an objectionable sudden spark advance and an objectionable although temporary knock for a short, though appreciable, interval of time.

Specifically, as the throttle is closed from the wide open position after acceleration in order to maintain a constant speed (the normal 4maneuver when driving a car) the spark vacuumsuddenly jumped from 0.35 inch Hg to 2 inches Hg as the manifold vacuum Vrose fro-m Vg inch HgA to 2%; inches Hg. A smooth increase from 1% inches I-Ig at 1A -inch Hg manifold vacuum to 7 inchesHg at 14 inches Hg manifold vacuum of this spark vacuum acting on the diaphragm is desired. If this increase is not exactly vwhat is wanted a combination of aloose spring and a tight tension spring acting at the rightangles will give the desired spark advance characterisf tics required for engines by movingthe ignition circuitbreaker plate. If this'increase in spar vacuum is not smooth but is broken then it is practically. impossible to obtain the right vcombinationof springs. to vgive the characteristic 2 Y spark advance for the particular engine demanded by the customer.

With no check valve gasoline actually finds its way into the air chamber nextto the diaphragm and the result is cumulative. This can be a very serious defect.

(B) The objection with (2) is that .a spring loaded check valve when accelerating from road load with a wide open throttle the ball" check snaps shut suddenly under the influence of the spring and thereby traps the high road load manifold vacuum inside the chamber neXt to the diaphragm so as to hold the spark in an advanced position. This high vacuum required some time to escape through the restriction leading-to the throat of the venturi.

Hence, during this appreciable interval of time there is an objectionable acceleration knock which is suiiic'ient to cause the customer to condemn the system in spite of any other advantages it might have.

I have discovered that the ideal solution is to use a gravity loaded small nylon4 ball with a free lift of from 1/2 inch to 41 inch. This ball is in a larger passage so that during acceleration as the vacuum (suction) in the venturi overcomes the inlet manifold vacuum there is air friction which lifts the ball and causes an appreciable delay during which the high vacuum of road load escapes before the check valve reaches its seat. What is known as tip in or acceleration knock is thus avoided.

Gravity causes the ball to descend and to open the restriction between the diaphragm chamber and the inlet manifold whenever the inlet manifold vacuum is equal to or exceeds the Venturi vacuum.

This check valve being held in its open position only by gravity quickly ascends to its closed position whenever air friction, due to the'flow of air past its sides due to the lower pressure in the venturi as compared with the manifold air pressure, overcomes the weight of this ball. The size of the rst air restriction leading from the diaphragm chamber into the venturi, the clearance in the passage around the nylon ball, the second air restriction between the ball and the first restriction, the location ofthe lip of the throttle with reference to the connection of the manifold suction and the check ball passage are all critical if ideal conditions are to be obtained.

At all times when driving a. car in traliic the throttle is moving, the load is changing and the speed of the engine is either decreasing or increasing. Static conditions are extremely rare'as the normal condition is one of change. If any changing condition creates a knock due to a too advanced spark or on the other hand if a too retarded spark causes sluggish operation and eX- cessive fuel consumption the spark characteristics are condemned.

Fig. 1 shows the preferred form of my invention when idling with the spark fully retarded.

Fig. 2 shows what happens when the throttle is closed from its wide open position to maintain a constant speed as the load is decreased following acceleration.

In Fig. 1, I is the air entrance, I2 is the Venturi into which discharges a small venturi. A nozzle, not shown, discharges into the small venturi. I4 is a restricted opening located immediately downstream of the throat of the venturi I2. IB is the opening in the wall of the mixture outlet immediately above the upstream lip of the throttle I8 when the throttle I8 Iis closed for idle. I'I` is an additional hole in the mixture outlet upstream of the opening I- and parallel thereto. is a pipe connecting the three openings i4, I0 and I1 with the chamber 22.-. The chamber 22 is bounded on the right by the diaphragm 24. This diaphragm is connected to the rod 26 with the circuit plate 28. A tight spring 30 connects. the stationary pin 32 with the moving pin 34 mounted on the plate 28. The loose spring 35 mounted on the pin 40 connects with the stationary pin 38 to control the advance of the spark. 42 is a cam which engages with the lever 44 mountedon the pin 46. A conducting spring 4,8 rotatesthe lever .44 clockwise and thus brings the berv rubbing block 50 into engagement with the cam 42Av as the cam 42 rotates` In the position shown the rubbing block 50 has parted company with the ca m 42y and the two tungsten points 512 and-,54 are in contact with each other so that electricity flows fromthe electrical conductor 5,8,` along the conducting spring 58 to the movabletungsten point 52 and so to the stationary tungsten point 54. Pin 4.6, andthe stationary tungsten` point 54 are both mountedV on the bracketrlll.

A slight adjustment on the bracket 00 is obtained by loosening the screws 52 and G4 in a well known manner.

A condenser 56 is provided to minimize the electrical heat that would otherwise burn the points 52 and 54.

68 is a pin which supports a nylon balll 'l0 in a passage 12. The nylon ball is just a littlel smaller than the passage 'l2 for a reason to be given in the description of Fig. 2. 74 is a slightly restricted opening connecting the passage 'l2 with the passage 'i5 immediately to the right of and below the restriction I4. The following .dimensions have been found satisfactory:

The nylon ball 'l0 is preferably .125 inch indiameter The passage 'I2 is .140 inch in diameter The clearance between the nylon ball I0 and the passage 'I2 isthus .007 inch Passage I6 is .070 inch in diameter Passage I'I is .035 inchin diameter Passage I4 is .038 inch in diameter Passage 'I4 is .041 inch invdiameter Description of Fig. 2

In Fig. 2* ABC represents the characteristic I have been able to secure with the above arrangef ment of parts and selection of dimensions given above. It represents the rise of spark vacuum acting on the diaphragm 24 as the manifold vacuum rises at some constant speed (2000 R. P. M.) as the load is decreased from Wide open throttle maximum load to road load.

Point B is critical because without the check valve the vacuum at A would only be .035 inch Hg at 0.5 inch Hg manifold vacuum and when the manifold vacuum rose to 21/2 inches Hg the spark vacuum would suddenly jump from 0.35 inch Hg to 2.0 inches Hg.

The distributor would have to be set for A and as a result B would give too much advance too soon. This would create a. knock If the distributor is set at A there is a gradual advance. Hence, without a check valve the point B was liable to cause a temporary knock to cure which the spark advance at A would be lowered somewhat and the fuel mileage would suffer accordingly.

With the ABCl characteristic, as shown, a very satisfactory fuel economy hasbeen secured,

The curved nature of the line ABC is. corrected by the spring arrangement asset forth in Westcott et al. Patent No. 2,503,645.

When the nylon ball having a specific gravity of 1/2 is replaced by an aluminum ball the clearance must be reduced to such an. extent that the restriction I4 must be made smaller.

What I claim is:-

1. A n ignition timing deviceV for an internal combustion engine comprising an ignition timer. an intake passageway of Venturi form, a throttle valve in said intake passageway downstream of said Venturi, a pressure controlled mechanism connected to said timer for advancing and retarding the spark, said mechanism comprising an air chamber having a pressure responsive moving wall, va first passage from saidchamber leading to the Venturi throat, a restriction in said passage, a second passagefrom said chamber to the air intake passageway adjacent said throttle and so located that it is substantially ver-tical and is( progressively subjected tothe engine suction at said throttle, a valve member having aspecic gravity less than three in said second passage, a clearance between the valve member and, said second passage so that the valve member is lifted by the air flow When the throttle is opened, a support member in said second passage adapted toi support said valve member-in a rst position, a seat located in saidsecond passage a substantial distance above saidI support member and above said valve member when said valve member is in said first position, said seat being adapted to be engaged by said valve member an appreciable interval of time after the throttlehas been opened.

2. A device as setl forth inuclaim l in whichthe valve member is spheroidal in form.

3. A device as set yforth* in claim 1 in which the valve member is a spheroid of nylon.

4. A device as set forth in claim 1 in which the valve member is a sphere of nylon.

5. AA device as set forth in claim 1 in which the valve member when in said rst position is located approximately 1/2 inch below said seat.

6. A device as set forth in claim 1, inwhich the throttle is of the butterfly type and inA which there is a restriction in said second passage located at the place in the intake passageway where the upstream lip of the throttlecreatesthe maximum suction during the initial stages of the'opening movement of said throttle.

7 Adevice as set `forthin claiml inwhich the throttle is of the butterfly type and inwhich there is a plurality of restrictions in parallel in said second passage located at the place in said second passage Where the upstream lip of the throttle creates the maximum suction during the initial stages of the opening movement of said throttle.

8. An ignition timing device for an internal combustion engine comprising an ignition timer, an intake passageway of Venturi form, a throttle valve in said intake passageway downstream of said venturi, a pressure controlled mechanism connected to said timer for advancing and retarding the spark, said mechanism comprising an air chamber having a pressure responsive moving Wall, a iirst passage from said chamber leading to the Venturi throat, a restriction in said passage, a second passage from said chamber to the air intake passageway adjacent said throttle and so located that it is substantially vertical and is progressively subjected to the engine suction at said throttle, a light Weight valve member in said second passage, a clearance between the valve member and said second passage so that the valve 6 member is lifted by the air flow when the throttle is opened, a support member in said second passage adapted to support said Valve member in a rst position, a seat located in said second passage a substantial distance above said support member and above said valve member when said valve member is in said rst position, said seat being adapted to be engaged by said valve member an appreciable interval of time after the throttle has been opened.

MELVIN STERNER,

REFERENCES CITED The following references are of record in the iile of this patent:

UNITED STATES PATENTS Number Name Date 2,365,313 Udale Dec. 19, 1944 2,365,768 Mallory Dec. 26, 1944 2,384,692 Olson et al Sept. 11, 1945 2,384,695 Olson Sept. 11, 1945

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