US3800754A

US3800754A - Engine fuel injection system

Info

Publication number: US3800754A
Application number: US00212036A
Authority: US
Inventors: L Carlson; G Reese; G Shank
Original assignee: Textron Inc
Current assignee: First National Bank of Minneapolis; Polaris Inc
Priority date: 1970-07-27
Filing date: 1971-12-27
Publication date: 1974-04-02
Anticipated expiration: 1991-04-02

Abstract

A fuel control system for low pressure fuel injection apparatus on an internal combustion engine. An impulse fuel pump operated by pulsating crankcase pressure delivers a desired quantity of fuel to the fuel port of the engine combustion chamber, and returns the unused portion of its output to the fuel tank through a bypass line. The quantity of fuel diverted to the bypass is controlled by a pressure actuated valve as a function of crankcase pressure, which is determined by throttle demand and engine speed, and by the pump output, as measured by pressure in the fuel line.

Description

Carlson et al. Apr. 2, 1974 ENGINE FUEL INJECTION SYSTEM 3,190,271 6/1965 Gudmundsen 123/73 c [75] Inventors: Lowell D. Carlson, Pencer; Gerald ii "28 Reese, Bromen; Gerald Shank, 3,610,213 10 1971 Giannini 123/140 MC Roseau, all of Minn.

[73] Ass1gnee: Textron Inc., Providence, R.I. Primary Examiner Laurence M Goodridge [22] Filed: Dec. 27, 1971 Attorney, Agent, or Firm-Merchant, Gould, Smith & 211 App]. No.: 212,036 Eden Related US. Application Data [63] Continuation-in-part of Ser. No. 58,431, July 27, 57 S R C l970, Pat. No. 3,707,143.

A fuel control system for low pressure fuel injection [52] 123/73 123/139 123/139 apparatus on an internal combustion engine. An im- 123/139 123/139 123/DIG- pulse fuel pump operated by pulsating crankcase pres- 23/140 MC sure delivers a desired quantity of fuel to the fuel port [51] Int. Cl. F02m 69/10 of the engine combustion chamber, and returns the [581 of Search 2 139 139 unused portion of its output to the fuel tank through a 123/139 139 A], 139 139 139 bypass line. The quantity of fuel diverted to the bypass 139 140 140 140 is controlled by a pressure actuated valve as a function 73 73 CB of crankcase pressure, which is determined by throttle I demand and engine speed, and by the pump output, as [56] References C'ted measured by pressure in the fuel line.

UNITED STATES PATENTS Gold et al. 123/140 MC 7 Claims, 2 Drawing Figures ENGINE FUEL INJECTION SYSTEM This is a continuation-in-part application of our pending application entitled Fuel Injection System for Two Cycle Engine, filed July 27, 1970 under Ser. No. 58,431 which issued on Dec. 26, 1972 as US. Pat. No. 3,707,143.

The invention is directed to a fuel control system for internal combustion engines, and is specifically directed to a fuel control system for low pressure fuel injection apparatus on two cycle internal combustion engines.

In our earlier patent application, we disclosed an improved fuel injection system which can be used on internal combustion engines without high pressure pumping equipment. That invention resides in the provision of a fuel accumulating cavity proximate the combustion chamber, and means for accumulating fuel in the cavity at a time other than during the intake cycle. When the intake cycle begins, the fuel cavity is opened, and its position proximate the combustion chamber enables the fuel to freely and instantaneously enter the combustion chamber in the absence of high pressure. The invention represents a significant advance in fuel injection system through its extremely-simple operation and elimination of the heretofore necessary high pressure equipment. 1

In the above-identified patent application we also disclosed a fuel metering system including an impulse fuel.

case which increases the pressure both to the fuel pump and to the pressure actuating metering valve. This has the effect of providing more fuel to the combustion chamber by way of the fuel cavity, which in turn increases revolutions of the engine per unit of time. A closing of the throttle effects a corresponding decrease in engine rpms by virtue of the decreased volume of air in the crankcase, which in turn decreases the pressure pulses to both the pump and control valve.

This type of fuel control system operates satisfactorily so long as the engine is capable of responding to an increase or .decrease in demand, as reflected by throttle position. However, as is frequently the case in connection with internal combustion engine, the vehicle to which motivating power is provided encounters extreme load conditions which preclude the engine from so responding. An example of this would be a snowmobile operating a relatively high rpms over essentially uniform terrain which suddenly encounters soft, deep snow. Under these conditions, speed of the snowmobile is decreased significantly, which effects a corresponding decrease in engine speed. For the fuel control system described above, decreased engine speed lessens the number of pressure pulses transmitted to the impulse pump and pressure actuated control valve which decreases the flow of fuel to the engine. This fuel de' crease can be offset to a degree by opening the throttle further to admit more air to the engine crankcase. However, the primary effect of such throttle movement is to increase only the magnitude of each pressure pulse; and if engine speed has been severely hampered by an increased load, the frequency of pulses will decrease commensurately and the engine will receive less fuel than it demands.

Our improved control system offers a significant solution to the problem of decreased fuel supply under the condition of an increased load where greater engine speed is demanded. As disclosed in conjunction with the low pressure fuel injection system described above, our fuel control system consists of an impulse pump operating by pulsating crankcase pressure, the output of which is delivered in part to the fuel accumulating cavity in the combustion chamber and in part to the fuel tank through a bypass line. A pressure actuated diverting valve is disposed in the bypass line to control the volume of fuel returned to the fuel tank. The diverting valve is controlled in a similar manner by rectified pulsating crankcase pressure, but is also responsive to the pump output, as measured by fuel pressure in the bypass line at a point upstream of the diverting valve.

The diverting valve is of the diaphragm type, defining opposed pressure chambers which respectively receive rectified crankcase pressure and pump output pressure to achieve a desired balance and valve position. Increased engine speed effects a commensurate increase in rectified crankcase pressure, which in turn tend to close "the valve and divert more fuel to the engine. However, the increased flow of fuel also increases fuel pressure on the outlet side of the pump, which opposes the crankcase pressure on the opposite side of the diaphragm. The desired balance between these two pressures is controlled by an adjustable spring or by varying the amount of crankcase pressure vented to atmosphere through an adjustable bleed valve. With this arrangement of components, a decrease in engine speed due to an increased load will effect a similar decrease in the frequency of pressure pulses from the crankcase. However, if the throttle remains open to admit more air to the crankcase, the result will be to deliver more fuel to the engine because the fuel line pressure has also undergone an appreciable drop. Consequently, the rectified crankcase pressure controls to close the diverting valve and to deliver an increased amount of fuel to the engine, bringing its level of power up to overcome the increased load.

Although the inventive principle is disclosed in conjunction with a two cycle internal combustion engine having a low pressure fuel injection system, it is applicable to other engine utilizing different fuel supply systems. The invention contemplates the control of fuel to an internal combustion engine as a-function of two variables: (a) engine demand, which may be evidenced by engine speed and throttle position; and (b) by the pump output, as evidenced by pressure on the outlet side of the fuel pump. If engine demand is relatively high and thefuel pump operates accordingly, a sufficient amount of fuel will be delivered to the engine. If

engine demand is high (as determined by throttle position) but the pump output is low, this condition would be sensed to further open the fuel control valve and deliver a sufficient amount of fuel to the engine. It will be appreciated that the supply and bypass configuration facilitates use of the inventive concept by offering a sufficient amount of fuel for any engine operating condition, and by diverting the proportional amount needed by the engine.

BRIEF DESCRIPTION OF TI-IE DRAWINGS FIG. 1 is a view of a fuel injected, two cycle internal combustion engine with a fuel control system embodying the inventive principle, part thereof being broken away; and

FIG. 2 is an enlarged schematic representation of the inventive fuel control system.

DESCRIPTION or THE PREFERRED EMBODIMENT In FIG. 1, an engine represented generally by the numeral 11 comprises an engine block 12 and head 13. Engine block 12 defines a crankcase chamber 14 in which a crankshaft 15 is mounted for rotation in the usual manner by a connecting rod 18.

A conventional fly wheel 19 is rotatably mounted on crankshaft I and carries a pulley 21 which drives an oil injecting pump 22 by an endless belt 23. Oil pump 22 receives a supply of oil from the engine crankcase, and pumps it through an oil line 24 to the main bearings (not shown) of crankchsaft for purposes of lubricatIon.

Opening on the inner cylindrical face of combustion chamber 16 is an air inlet port 25 which communicates with atmosphere through an air horn 26. A butterfly valve 27 is rotatably disposed in the air horn 26 and serves to vary the volume of air entering therein in the usual throttling fashion. Butterfly valve 27 is rotatable by a manual control (not shown) to vary the speed of engine 11, as described below.

Also opening on the inner cylindrical face of combustion chamber 16 are an air transfer port 28 and an exhaust port 29, the former of which communicates with the engine crankcase 14 by a passage formed in the engine block 12. As indicated in FIG. 1, the top of transfer port 28 is disposed slightly below the top of exhaust port 29 with respect to the cylinder axis, and air inlet port is located a distance below transfer port 28. A threaded opening is formed in the top of cylinder head 13 to receive a spark plug 31.

Fuel is admitted to combustion chamber 16 from a fuel accumulating cavity 32 which is formed on the inner cylindrical face of combustion chamber 16. The size of cavity 32 is exaggerated in FIG. 1 for purposes of clarity. As described more fully in the aforementioned pending patent application, cavity 32 is preferablyconcave in shape and has a relatively large crosssectional area as compared to its shallow depth. This configuration permits fuel accumulated in the cavity 32 to freely and instantaneously discharge into the combustion chamber 16 when uncovered by piston 17.

With respect to the cylindrical axis of combustion chamber 16, cavity 32 is disposed between air inlet port 25 and the 'top of transfer port 28 and is of sufficient size to hold a fresh charge of fuel for subsequent vaporization-and combustion in the combustion chamber 16. Cavity 32 is connected to a fuel control system, represented generally by the numeral 33, by a passage 34 in cylinder head 13 which includes a ball type check valve 35.

With additional reference to FIG. 2, fuel control sys tem 33 comprises an impulse type fuel pump 36 which communicates with crankcase chamber 14 through a conduit 37, and is actuated by the pulsating pressure generated in the chamber 14 by the reciprocal action of piston 17. It will be appreciated that the operation of pump 36 varies as a function of engine speed, which determines the number of pressure pulses generated per unit of time; and also as a function of the position of throttle valve 27, which controls the volume of air entering crankcase chamber 14 and thereby determines the magnitude of the pressure pulses generated.

Pump 36 has an inlet 38, which receives fuel from a tank 39 through a conduit 41. The pumped fuel passes through an oulet 42, all or a portion thereof being directed into a conduit 43 or a conduit 44 by a Y- connector 45. Conduit 43 is connected to the fuel passage 34, and conduit 44 is connected to an inlet 46 of a pressure actuated control valve 47. A conduit 48 leads from an outlet 49 of the control valve 47, and serves as a bypass to return fuel to tank 39.

Control valve 47 has a second inlet 51 which communicates with pulsating crankcase pressure through a conduit 52, T-connector 53 and conduit 37. Conduit 52 includes a check valve 54, which rectifies the pulsating crankcase pressure and admits only the positive pressure pulses to the control valve 47 in the known manner.

With specific reference to FIG. 2, pressure actuated control valve 47 comprises a housing 55 within which a diaphragm 56 defines first and second

control pressure chambers

57 and 58, respectively. Inlet 46 communicates with pressure chamber 58, and inlet 51 communicates with pressure chamber 57.

Operating in conjunction with the pressure chamber 57 is a threaded member 59 which adjustably carries a diaphragm biasing spring 61. Threaded member 59 has a bleed passage 62 for venting the air in chamber 57 to atmosphere. A needle type idler valve 63 operates in conjunction with bleed passage 62 to control the rate at which air is vented from the pressure chamber 57.

Diaphragm 56 carries a needle valve 64 which operates in association with a threaded valve seat member 65, which also defines the outlet 49.

It will be appreciated that the position of needle valve 64 is determined by the respective pressures in

control chamber

57 and 58, the force exerted by biasing spring 61 and the bleed rate established by needle valve 63. The position of needle valve 64 in turn controls the flow of fuel into the return conduit 48, and thereby determines the quantity of fuel which passes through conduit 43 and into the cavity 32 for subsequent combustion.

As will be discussed in greater detail below, it is of importance that the pressure actuated control valve 47 sense the outlet pressure of impulse pump 36 as well as the rectified pulsating pressure of crankcase chamber The broad function of fuel control system 33 is to control or meter fuel to the engine 11 as a function of engine demand. In connection with the low pressure fuel injection apparatus disclosed, and as more fully described in the aforementioned pending patent application, its function is to meter fuel to the cavity 32 in accordance with engine demand, and at a time other than during the intake cycle of the engine. This period of time is much longer than the intake cycle itself, giving the fuel ample time to accumulate in cavity 32 for sub sequent discharge when the cavity is uncovered by piston 17. It is this concept of accumulating fuel during the off-intake cycle at a point proximate the combustion chamber which permits low pressure fuel injection and thereby eliminates the need for high pressure apparatus.

Piston 17 is shown in FIG. 1 at a position immediately after ignition has occurred. Combustion drives the piston 17 downward until it uncovers the exhaust port 29 to discharge combusted gases therefrom. Continued downward movement of the piston 17 uncovers the air transfer port 28, admitting air into the combustion chamber 16 from the crankcase. With further downward movement, the cavity 32, which has already accumulated the fuel charge, is uncovered and the fuel discharges freely and instantaneously into the combustion chamber 16. At this point, piston 17 reverses its movement and travels upwardly to compress the new fuel and air charge until ignition occurs.

Crankcase chamber 14 is an essentialy closed chamber except during the time piston 17 uncovers air inlet port to admit air therein. Throttle valve 27, which is manually controlled by the engine operator, determines the volume of air admitted by its position. Once the air inlet port 25 is closed, the captured air is compressed by the underside of piston 17 to generate a positive pressure pulse to impulse pump 36 and pressure actuated control 47. Pump 36 thus displaces a discrete quantity of fuel which is disengaged through outlet 42 and directed into conduit 43 and/or 44 as described below. This positive pressure pulse has a magnitude sufficient to overcome the spring in check valve 54, and it is therefore transmitted to the pressure chamber 57 in control valve 47.

The generation of a positive pressure pulse continues until piston 17 uncovers air transfer port 28. At this point, pressure in the crankcase 14 decreases as air is transferred to the combustion chamber 16; and this pressure decreases further as piston 17 moves upwardly to close air transfer port 28 and expand the volume of crankcase chamber 14. Such movement reverses the pressure differential with respect to impulse pump 36 to prepare it for the next positive displacement. The reverse pressure differential is also sensed by check valve 54, which closes to preclude a decrease in pressure in chamber 57. Check valve 54 thus serves as a half-wave rectifier and, in conjunction with needle valve 63 and spring 61, gives rise to a control pressure in chamber 57 indicative of engine demand.

The opposed face of diaphragm 56 senses the fuel pressure in chamber 58, which changes as a function of pressure generated at the outlet of pump 36. When the output of pump 36 is low (as determined by engine speed and throttle position) the opposing force generated in chamber 58 will be correspondingly low; and this force will increase as the output of pump 36 increases.

The desired balance of forces across diaphragm 56 is brought about by adjustment of the needle valve 63 and biasing spring 61. With the pressure actuated control valve 47 properly adjusted, rectified crankcase pressure in chamber 57 will tend to close needle valve 64, whereas the output pressure generated by pump 36 will tend to pen the needle valve 64; and a balance between the two will be reached to proportionately meter the proper quantity of fuel to the engine 11 and return the remainder to the tank 39. At idling speed of the engine 1 1, spring 61 provides the primary force in establishing an idle position of needle valve 64. At lower engine speeds the pressure in chamber 57 increases slightly to increase the amount of fuel returned to tank 39, but the impulse pump 36 produces a commensurate increase in fuel to the chamber 58, which provides an accurate balancing force to preclude the complete closing of needle valve 64. In the absence of this balancing force, the entire output of pump 36 would be directed to engine 11, which would be more than the engine demand. As throttle valve 27 is manually opened to admit more air to the crankcase chamber 14, the rectified control pressure in chamber 57 increases, as does the fuel pressure in chamber 58 by virtue of an increased output of pump 36. The resulting balance of forces causes needle valve 64 to offer a greater restriction to fuel entering the return line 48, thus resulting in an increased supply of fuel to engine 11. This balanced operation continues throughout the operational range of engine 11 so that fuel is properly metered by the control system 33 as a function of current engine speed and demand.

The unique operation of fuel control system 33 occurs under the condition where engine speed has been relatively high, as determined by an open position of throttle valve 27; and where such engine speed is decreased not by closing throttle valve 27 but by an increased load on the engine. Because engine revolutions have decreased, the frequency of pressure pulses generated within crankcase chamber 14 decreases also. As a result, the output of pump 36 decreases, as does the rectified control pressure in chamber 57. In the absence of control chamber 58, the result would be to provide less fuel to engine 11, even though throttle valve 27 remains in a wide open position. However, control chamber 58 senses the diminished output of pump 36, and the opposing force generated therein undergoes a commensurate decrease. Because throttle valve 27 is wide open, maximum air is drawn into the crankcase chamber 14 and the magnitude of pressure pulses remains high although the frequency does not. Rectified crankcase pressure in chamber 57 is sufficient to overcome the decreased fuel pressure in chamber 58, and the result is closing of the needle valve 64. Thus, rather than metering a lesser flow of fuel to engine l 1 under the increased load condition, fuel control system 33 responds to the condition by continuing a substantial flow of fuel so that engine 11 can quickly recover power through increased engine speed.

We claim:

1. A fuel control system for an internal combustion engine having a crankcase sealably communicating with a piston and throttle means for varying the volume of air entering the crankcase, the control system comprising:

a. fuel pumping means for providing a fuel output which varies as a function of engine speed, the fuel pumping means having an inlet adapted for connection to a fuel supply and an outlet;

b. conduit means for connecting the pumping means outlet to the engine and to the fuel supply;

c. and, control means sensitive to the output pressure of the pumping means and to rectified crankcase pressure for controlling the amount of fuel delivered from the pumping means to the engine and diverting the remainder to the fuel supply as a function of the difference between said pressures.

2. The control system defined by claim 1, wherein the conduit means comprises a first conduit connecting the pumping means outlet to the engine and a second conduit connecting the pumping means outlet with the fuel supply, the control means being constructed and arranged to meter a portion of fuel from the pumping means into the first conduit means in accordance with said pressure difference, and to divert the remaining portion into the second conduit means.

3. The control system defined by claim 2, wherein the control means comprises:

a. a housing including diaphragm means defining first and second opposed control pressure chambers;

b. valve means operably connected to the diaphragm means for proportioning fuel into the first and second conduit means;

c. the first control pressure chamber communicating with the rectified crankcase pressure;

d. and the second control pressure chamber communicating with fuel pressure in said first and second conduit means upstream of said valve means.

4. The control system defined by claim 3, wherein:

a. the valve means is constructed and arranged to direct all fuel into the second conduit means when closed;

b. and the control means further comprises adjustable biasing means for normally closing the valve means.

5. The control system defined by claim 3, wherein:

a. the first control chamber communicates with the crankcase through third conduit means including check valve means for permitting, only positive pressure to be conducted to the first control chamber;

b. and the first control chamber further comprises a bleed passage communicating with the atmosphere, and means for variably restricting the bleed passage.

6. The control system defined by claim 3, wherein:

a. the second control chamber forms part of the second conduit means;

b. and the valve means is disposed in the second control chamber.

7. A fuel control system for an internal combustion engine having a crankcase sealably communicating with a piston and throttle means for varying the volume of air entering the crankcase, the control system comprising:

a. an impulse pump operably connected to the crankcase for operation by pulsating pressure therein, the pump having an inlet adapted for connection to a fuel supply and an outlet;

b. pressure actuated valve means comprising 1. a housing including a diaphragm defining first and second pressure control chambers;

2. the first control chamber having an inlet, a bleed passage communicating with the atmosphere and means for adjustably restricting the bleed passage;

3. the second control chamber having an inlet and a valve seating member defining an outlet;

4. a valve closure member carried by the diaphragm and operable in conjunction with the valve seating member;

5. and spring means for biasing the valve closure member toward the seating member;

c. first conduit means connecting the pump outlet with the engine;

(1. second conduit means connecting the pump outlet to the inlet of the second control chamber, and connecting the outlet of the second control chamber to the fuel supply;

e. and third conduit means including a check valve for connecting the crankcase with the first control chamber.

Claims

1. A fuel control system for an internal combustion engine having a crankcase sealably communicating with a piston and throttle means for varying the volume of air entering the crankcase, the control system comprising: a. fuel pumping means for providing a fuel output which varies as a function of engine speed, the fuel pumping means having an inlet adapted for connection to a fuel supply and an outlet; b. conduit means for connecting the pumping means outlet to the engine and to the fuel supply; c. and, control means sensitive to the output pressure of the pumping means and to rectified crankcase pressure for controlling the amount of fuel delivered from the pumping means to the engine and diverting the remainder to the fuel supply as a function of the difference between said pressures.

3. The control system defined by claim 2, wherein the control means comprises: a. a housing including diaphragm means defining first and second opposed control pressure chambers; b. valve means operably connected to the diaphragm means for proportioning fuel into the first and second conduit means; c. the first control pressure chamber communicating with the rectified crankcase pressure; d. and the second control pressure chamber communicating with fuel pressure in said first and second conduit means upstream of said valve means.

4. The control system defined by claim 3, wherein: a. the valve means is constructed and arranged to direct all fuel into the second conduit means when closed; b. and the control means further comprises adjustable biasing means for normally closing the valve means.

5. and spring means for biasing the valve closure member toward the seating member; c. first conduit means connecting the pump outlet with the engine; d. second conduit means connecting the pump outlet to the inlet of the second control chamber, and connecting the outlet of the second control chamber to the fuel supply; e. and third conduit means including a check valve for connecting the crankcase with the first control chamber.

5. The control system defined by claim 3, wherein: a. the first control chamber communicates with the crankcase through third conduit means including check valve means for permitting only positive pressure to be conducted to the first control chamber; b. and the first control chamber further comprises a bleed passage communicating with the atmosphere, and means for variably restricting the bleed passage.

6. The control system defined by claim 3, wherein: a. the second control chamber forms part of the second conduit means; b. and the valve means is disposed in the second control chamber.

7. A fuel control system for an internal combustion engine having a crankcase sealably communicating with a piston and throttle means for varying the volume of air entering the crankcase, the control system comprising: a. an impulse pump operably connected to the crankcase for operation by pulsating pressure therein, the pump having an inlet adapted for connection to a fuel supply and an outlet; b. pressure actuated valve means comprising