US3126879A - Fuel injection control mechanism - Google Patents

Description

March 31, 1964 c. R. CANFIELD, JR

FUEL NJEcTIoN CONTROL MECHANISM Filed March 2v. 1961 United States Patent iiice 3,126,879 Patented Mar. 31, 1964 iiiiinois Fiied Mar. 27, 1961, Ser. No. 98,449 3 Claims. (Cl. 12S-140) This invention relates to a deceleration cut-off mechanism vfor a f-uel injection system.

The fuel injection system with which the present invention is used is adapted to deliver metered charges of fuel in sequence to a plurality of engine cylinders. The fuel delivery nozzles are mounted in the air-intake manifold and fuel is injected in time with the opening of the respective intake valves. One major advantage of a highpressure fuel injection system of this type is that each charge of fuel is completely ingested into its respective cylinder during the time the intake valve is open, and there is little or no wetting of the inner wall of the airintake manifold.

The sharp cut-oif capability of the system is useful in controlling the smog or unburned hydrocarbon output of the engine. A major portion of the smog formed by an automotive vehicle engine is generated during the deceleration portion of its operating cycle. Fuel cut-off devices for carburetors, operable during deceleration, are well known in the art, but in a carbureted system, the inner wall of the air intake manifold is wetted with fuel. Consequently, even if the fuel is completely cut off during deceleration, the fuel remaining on the inner wall may enter the combustion chambers as a non-combustible mixture and be exhausted as unburned hydrocarbons.

It is an object of the present invention to provide an improved fuel injection control mechanism effective to cut off completely the delivery of fuel through the nozzles during deceleration, with the resultant fuel economy and elimination of smog.

It is another object to provide a control mechanism for a fuel injection pump comprising a movable cam for metering the output of the pump and absolute manifold pressure responsive means for moving the cam through an operating range, said cam being formed so as to completely cut oif the fuel output of the pump for a portion of the operating range.

It is a more particular object to provide a movable cam and a cam follower connected to control the fuel output of an injection pump, a manifold pressure responsive servomotor connected to move said cam in accordance with changes in ambient pressure, whereby said cam is moved throughout its operating range in accordance with variations in absolute manifold pressure, the cam profile being formed with a cut-out portion operable with said cam follower to cut off the supply of fuel from said pump when the cam has been moved into the deceleration portion of its operating range.

The invention consists of the novel constructions, arrangements, and devices to be hereinafter described and claimed for carrying out the above-stated objects and such other objects as will appear from the following description of a preferred form of the invention, illustrated with reference to the accompanying drawings, wherein:

FIG. 1 is a longitudinal sectional view, partially in schematic form of the fuel injection control mechanism of the present invention including a movable cam; and

FIG. 2 is an enlarged View of the cam shown in graphic form.

Like characters of reference designate like parts in the several views.

Referring to FIG. 1, the improved control mechanism of the present invention is designated generally by the numeral and is adapted to control the output of a fuel injection pump 11. The control mechanism 1t) comprises a computer or integrating section 12, a manifold pressure responsive servomotor 13, and a reference pressure servomotor 14.

The computer section 12 comprises a housing or casing portion 15, a longitudinally movable cam 16, a cam follower 17, a cam follower arm 18, a roller carriage 19, and a supporting rail 20. The cam 16 is formed with a cam surface 21 which engages the cam follower 17, and is movably supported on the rail 20 by the roller carriage 19. The cam 16 is connected to the servomotor 13 by means of a connecting shaft 22 and to the servomotor 14 by means of a connecting shaft 23. The cam 16 is formed with a slot 24 for receiving a screw 25 which is attached to the shaft 22 and is also formed with an access opening 26 through which a screw 27 connects the cam 16 to the shaft 23. A tie bar 28 is connected to the screws 25 and 27 and interconnects the shafts 22 and 23 so that they move as a unit.

The manifold pressure responsive servomotor 13 comprises a casing 36B formed with an internal cavity 31, a flexible diaphragm 32, and a spring 33. The iiexible diaphragm 32 is connected to the connecting shaft 22 by means of a machine screw 34 and is adapted to be moved under the influence of manifold pressure and the force eX- erted by the spring 33. The interior of the casing 30 is connected by means of a conduit 35 to the air-intake manifold 36 of the engine.

The reference pressure servomotor 14 comprises a casing 4t? formed with an internal cavity 41, a exible diaphragm 42 and a spring 43. The diaphragm 42 is connected to the connecting shaft 23 by means of a machine screw S4 and is adapted to be moved under the influence of the manifold pressure responsive servomotor 13, the spring 43 and changes in ambient or atmospheric pressure. The interior of the casing iii is connected by means of a conduit 45 to a reference pressure source 46, such as a vacuum pump. Alternatively, the interior of the casing 4i) may be evacuated to some predetermined low pressure and permanently sealed, or the diaphragm 42 may be replaced by a suitable metallic aneroid bellows of equivalent effective area.

The pump 11 includes a metering shuttle or valve 50 adapted to be controlled by the cam 16. The cam follower arm 18 is pivotally mounted on the casing 15 by means of a pin S1 and is connected to the metering Valve by means of a longitudinally movable link 52. The fuel injection pump 11 is connected to deliver fuel through a plurality of conduits 53 to nozzles 54 mounted in the air-intake manifold 36 adjacent respective air-intake valves. A throttle valve 55 controls the admission of air into the air-intake manifold 36.

Referring to FIG. 2, there is illustrated an enlarged View of the cam 16 on which is superimposed a graph of its operating range. The cam 16 is formed with a cutout portion 60, the purpose of which will now be described. The cut-out portion is dened by a horizontal cam surface 61 and a vertical step 62.

The normal operating range of the cam varies from approximately zero inches of mercury at wide open throttle to approximately twenty-one inches for fast idle conditions. Under normal idle condition with closed throttle, the manifold vacuum may be eighteen-nineteen inches of mercurq. For deceleration conditions, when the engine is turning over at high speed and the throttle is closed, the vacuum may increase to as much as twenty-two to twentysix inches or more of mercury.

The pump percentage output increases substantially linearly frorn idle condition to wide open throttle. There may be some minor variations in this rate of output because the cam 16 is designed to match the characteristics of a particular engine. The output of the pump is something less'than 20% at twenty inches of mercury and is nearly'100% at wide open throttle.

Operation In operation, vthe cam16 is moved longitudinally by the servomotor 13'which responds to changes in pressure within the air intake manifold '36, corresponding .to thevdegree of throttle valve opening and engine speed. The force developed by the servomotor 13 is determinedby the differential in pressure across the diaphragm 32 and the force of the spring 33. As the cam 16 is moved longitudinally, the cam .follower 17 ridesup and down the inclinedcam surface 21 and the cam follower arm 1S acts on the metering` valve 50 to control the fuel output in accordance with engine demand as determined'byA manifold pressure. The reference pressure servomotor 14 exerts abias force upon the servomotor 13` that varies with changes in atmospheric pressure. The bias force is the resultant oftheforce due to the differential in pressure across the diaphragm 42 and the force exerted by the spring, 43. The diaphragms 32 and 42 are of approximately the same diameter so that any changes in ambient pressure, such as due to changes in altitude, are effectively cancelled out. Thecam 16, therefore, is moved as a function of absolute manifold pressure. The diaphragm 32 is actually somewhat larger than diaphragm 42 so as to correct for changes in exhaust back pressure.

In its normal operating range, the cam follower 17 remainsin contact with the cam surface 21 and causes the pump to deliver some fraction of its potential output which is equal to the road loadk fuel requirement of the engine, For deceleration condition, however, when the engineis turning over-at substantial speed and the throttle valve is closed, the pressure in the manifold 36 decreases below that at idle and the cam 16is moved farther to the left than normal. When the cam is moved to this portion of its operating range, the cam follower 17 drops down into the cut-out portion 60 and rolls along the cam surface 61. The cam surface 61 lies below the zero output level of the pump 11, and the fuel delivery is completely cut olf.

The fuel remains cut olf until the speed of the engine decreases to nearly idle speed. This may occur, for example, at.a road speed of approximately fifteen m.p.h. The step 62 inhibits the cam follower 17 from rolling back up onto the cam surface 21. This means that the absolute pressure in the manifold 36 must actually increase above that at which the cam follower 17 dropped into the cut-off range. Once the cam follower 17 has rolled back up on the normal road load portion of the cam surface 21, the pump 11 delivers the required fuel and the engine, which was being turned over at an r.p.m. proportional to vehicle speed, resumes normal combustion and operation.

There has been provided byV this invention an approved absolute manifold pressure control device for a fuel injection pump including a movable cam with a cani surface defining a normal operating range and a deceleration range. The normal operating range is defined by an inclined cam surface effective to vary the output of the pump as the cam is moved longitudinally. The deceleration range is defined by a vertical step adjacent the inclined surface and a longitudinal at surface. The-absolute manifold pressure controlsinsure'that the operation of the control system as determined by the position of the cam-remains the same regardless of changes in ambient pressure or changes in altitude of the vehicle;

It is to be understoodthat theinvention is not to be limited to the specic constructions andA arrangements shown and described, except only insofar as the claimsy may be so limited, as it will be understood to those skilled in the art that changes may be made without departing from the principles of the invention.

I claim:

1. In a control system for a fuel metering device adapted to supply fuel to an internal combustion engine having an air-intake manifold, the combination of a movable cam follower connected to control the output of the device, a movable cam engaged by said cam follower,

said movable cam having a cam surface including means defining a cut-out portion for completely cutting olf the fuel supplied by said device when said cam follower is engaged with said cutout portion, a first servomotor connected to the air-intake manifold of the engine and to said cam for exerting a metering force thereon for moving said cam in accordance with changes in pressure within the air-intake manifold, a second reference pressure servomotor also connected to said cam for exerting` a metering force thereon to adjust the position of saidcam in accordance with changes in ambient pressure, a connecting shaft directly interconnectingV both said servornotors whereby said cam is moved to an equilibrium position.

2. In a control system for a fuel metering device adapted to supply fuel to an internal combustion engine having an air intake manifold, the combination comprising: a cam follower operatively connected with said device to control the output thereof; a movable cam connected to control the output of the device, said cam having an inclined cam surface and a substantially horizontal cam surface, both of said cam surfaces being adapted to engage said cam follower, said inclined cam surface corresponding to a normal operating range between idle and full throttle, said horizontal cam surface-corresponding to a deceleration range wherein the output of the device is completely cut off; a first actuator connected to the air intake manifold of the engine and -to said cam for exerting a metering force thereon for moving. said'cam in accordanceV with changes in pressure within the air intake manifold; a second actuator also connectedl to said cam for exerting arnetering force thereon to adjust the position of said cam in accordance with changes in ambient pressure, said cam being positioned between said first and second actuators and adapted for longitudinal movement; shaft means directly interconnecting said cam and said actuators, said cam, shaft interconnecting means and actuators being constructed and arranged for joint linear reciprocation, whereby said cam ismoved to an equilibrium position of the metering forces exerted by said actuators; and means for, inhibiting the return of said cam follower to said normal operating range after it has been moved into said deceleration range.

3. A control system as defined in claim 2 wherein said means for inhibiting the movement ofsaid cam follower comprises a sharply stepped portion on-said cam adapted to engage said cam follower when moving from the-deceleration range back to the normal operating-range.

References Cited in the file of this patent UNITED STATES PATENTS 2,378,037 Reggio June l2, 1945 2,667,840 High Feb. 2, 1954 2,670,724 Reggio Mar. 2, 1954 2,852,011 Pringham Sept. 16, 1958 2,984,232 Arndt et al May 16, 1961 3,020,776 May etal Feb. 13, v1962 FOREIGN PATENTS 854,675 Great Britain Nov. 23, 1960

Claims (1)

1. IN A CONTROL SYSTEM FOR A FUEL METERING DEVICE ADAPTED TO SUPPLY FUEL TO AN INTERNAL COMBUSTION ENGINE HAVING AN AIR-INTAKE MANIFOLD, THE COMBINATION OF A MOVABLE CAM FOLLOWER CONNECTED TO CONTROL THE OUTPUT OF THE DEVICE, A MOVABLE CAM ENGAGED BY SAID CAM FOLLOWER, SAID MOVABLE CAM HAVING A CAM SURFACE INCLUDING MEANS DEFINING A CUT-OUT PORTION FOR COMPLETELY CUTTING OFF THE FUEL SUPPLIED BY SAID DEVICE WHEN SAID CAM FOLLOWER IS ENGAGED WITH SAID CUTOUT PORTION, A FIRST SERVOMOTOR CONNECTED TO THE AIR-INTAKE MANIFOLD OF THE ENGINE AND TO SAID CAM FOR EXERTING A METERING FORCE THEREON FOR MOVING SAID CAM IN ACCORDANCE WITH CHANGES IN PRESSURE WITHIN THE AIR-INTAKE MANIFOLD, A SECOND REFERENCE PRESSURE SERVOMOTOR ALSO CONNECTED TO SAID CAM FOR EXERTING A METERING FORCE THEREON TO ADJUST THE POSITION OF SAID CAM IN ACCORDANCE WITH CHANGES IN AMBIENT PRESSURE, A CONNECTING SHAFT DIRECTLY INTERCONNECTING BOTH SAID SERVOMOTORS WHEREBY SAID CAM IS MOVED TO AN EQUILIBRIUM POSITION.

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