US3672339A

US3672339A - Fuel injection apparatus

Info

Publication number: US3672339A
Application number: US13633A
Authority: US
Inventors: Jeffrey M Lazar
Original assignee: Honeywell Inc
Current assignee: Honeywell Inc
Priority date: 1970-02-24
Filing date: 1970-02-24
Publication date: 1972-06-27
Anticipated expiration: 1989-06-27

Abstract

A fluidically controlled fuel injection system wherein fuel is delivered to the engine in pulses, the repetition rate of the pulses corresponding to engine speed, and the duration of the pulses being determined primarily by engine manifold vacuum. Pneumatic means may be provided to compensate the fuel injection system for variations in air temperature, engine temperature, and atmospheric pressure.

Description

United States Patent Lazar 1 1 June 27, 1972 [541 FUEL INJECTION APPARATUS 3.302.935 2/1967 York ..137/a1.s x

I 3,388,898 6/1968 Wyczalek m] Imam" 3,529,612 9/1970 Rausch [73] Assignee: Honeywell Inc., Minneapolis, Minn. 3,392,739 7/1968 Taplin et a1 1 37/82 X [22] Flled: 1970 Primary Examiner-Wendell E. Burns [21] Appl. No.: 3,633 Assistant Examiner-A. M. Zupcic Attorney-Charles J. Ungemach, Ronald T. Reiling and 52 us. (:1. ..1z3/119 R, 261/DIG. 159. 123/010. 10, Charles! 123/97 B, 123/103 51 1 1m. c1 .rozm 7/00, F02d 31/00 [571 ABSTRACT [58] Field of Search "123/119 A fluidically controlled fuel injection system wherein fuel is 137/815 82; 261N316 69 delivered to the engine in pulses, the repetition rate of the pulses corresponding to engine speed. and the duration of the [56, References Cited pulses being determined primarily by engine manifold UNITED STATES PATENTS vacuum. Pneumatic means may be provided to compensate the fuel injection system for variations in air temperature. en- 3,54s,794 12/1970 Lazar ..123/D|G. 10 sinetemperature, and atmospheric pressum 3,552,365 l/l971 Williams... 3,556,063 H1971 Tuzson I 23/DlG. l0 7 Claims, 6 Drawing Figures PRIMARY FUEL PATENTED I972 3.672, 339

SHEET 1 BF INVENTOR. JEFFREY M. LAZAR BY f- ATTORNEY PATENTED Z IE? 3. s72 339 SHEET 2 BF 4 PRlMARY FUEL VALVE 9 INVENTOR.

J JEFFREY M. LAZAR ATTORNE PATENTEDJUNZ? m2 3.672.339 sum 3 or 4 FIG. 3

MAX. 1

FUEL DELIVERY RATE MANIFOLD VACUUM in HQ.

, INVENTOR. JEFFREY M. LAZAR ATTQRNJ This invention relates generally to fuel injection apparatus, and more specifically to fluidically controlled fuel injection systems for internal combustion engines.

It has long been recognized that fuel injection of spark igni' tion internal combustion engines ofl'ers significant advantages over conventional carburetion. These advantages include higher volumetric efficiency, more uniform distribution of mixture among the cylinders, improved fuel economy, better cooling of inlet valves, and lack of need for preheating air to provide vaporization, which in turn permits the use of higher compression ratios and the development of higher output power. Fuel injection systems have been successfully in automobile racing engines and in aircraft engines, where they offer the additional advantage of freedom from icing. Although fuel injection systems have also been used in certain high performance, limited production sports cars, with a few exceptions they have not seen general use in standard production car engines.

The greater complexity and higher cost of a fuel injection system over a comparable carburetor have been the principle reasons why fuel injection systems have not received more general use. Over the years, many different fuel injection systems have been proposed, but these systems have in general required additional fuel pumps, fuel metering devices, valves, injectors, and associated pipes, tubes and wiring. Some systems have employed electrically operated injectors which require solenoids, timing switches, and even electronic computers for their operation. The inclusion of these devices has contributed to higher costs and lower reliability. Additionally, in order to realize the potential benefits of any fuel injector system, it must be capable of accurately metering the proper quantity of fuel to the cylinders. To meet this requirement, many of the components of the prior art fuel injection systems have had to be specially machined to very close tolerances, which leads to high costs. In addition to the high cost of manufacture, many of these systems have required elaborate and precise adjustment and calibration for proper operation.

Because of growing concern over controlling exhaust gas emissions of automobile engines, there has been renewed interest in fuel injection systems. It is felt that the more accurate fuel metering possible with fuel injection allows better control over the combustion in the individual cylinders, and it is therefore possible to keep production of pollutants at a minimum.

SUMMARY OF THE INVENTION In the present invention the applicant has provided a fuel injection system that overcomes the main disadvantages heretofore associated with fuel injection systems. The applicant has provided a system wherein the fuel metering functions are performed accurately and reliably by fluidic components, with a minimum of moving mechanical parts. Critically close manufacturing tolerances are not required, and complicated and frequent calibrations and adjustments are not needed.

Applicant's invention comprises means for generating a train of fluid pulses having frequency indicative of engine speed, means for varying the duration of the fluid pulses primarily according to the pressure in the engine air intake passage, fuel valve means for energization by the fluid pulses, and injector means for supplying fuel to the engine upon energization ofthe fuel valve means.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a schematic representation of one embodiment of applicant's invention;

FIG. 2 is a schematic representation of a second embodiment of applicant's invention;

FIG. 3 is a cross sectional view of a variable fluidic capacitor which may be used in applicants invention;

FIG. 4 is a cross sectional view of a fuel valve used in one embodiment of applicant's invention;

FIG. 5 is a graph showing the operation of applicants invention; and

FIG. 6 is a cross sectional view of another fuel valve which may be used in applicants invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, reference numeral I0 designates an internal combustion engine incorporating a fuel injection system according to the present invention. Engine 10 includes an engine block 11, an air intake passage 13, and an air cleaner I2. Positioned inside air intake passage 13 is a conventional throttle butterfly valve 14, and a venturi tube 16. An air intake passage 17 provides air for engine idling.

Fluid pulses for die operation of the fuel injector system are provided by pulse generating means 30, which comprises a wheel 31 attached to a shaft 32, and a pair of

coaxial conduits

33 and 34. In this embodiment, shaft 32 is geared (not shown) to run at one half engine crank shaft speed. For convenience, wheel 31 may be attached to the ignition distributor shaft (not shown). Wheel 31 has a first portion having a first radius extending through of arc, and a second portion having a second larger radius extending through the remaining 180 of arc.

Coaxial conduits

33 and 34 are mounted in close proximity to the circumference of the larger portion of wheel 31v Air at a working pressure from an air supply 35 is supplied to conduit 33 by conduit 36. When wheel 31 is in the position shown, air escaping from conduit 33 is reflected back by the circumference of wheel 31, and enters conduit 34. When shaft 32 has rotated through an angle so that the smaller portion of wheel 31 is nearest conduit 33, the pressurized air therein is free to escape, and does not reflect back into conduit 34. Pulse generator 30 therefore produces a square wave or a series of pressure pulses in conduit 34, whose amplitude is determined primarly by the pressure of the air from supply 35, and whose frequency is equal to the rotational speed of shaft 32 which is proportional to engine speed.

The fluid pulses thus generated are supplied to pulse modifying means 40, for pulse duration modulation according to engine fuel requirements. Pulse modifying means 40 comprises a fluid amplifier 4] and a variable capacitor 45. Fluid amplifier 41 is a bistable, or wall attachment type amplifier, the operating principles and construction of which are well known to those skilled in the art. Amplifier 41 comprises a power nozzle a, a pair of outlet passages 12 and c, a pair of control ports d and e, and a pair of vents 42 and 43. Air at a work ing pressure is applied to power nozzle 0, causing a power stream to pass through the amplifier and out either outlet passage b or outlet passage c. The air for energizing power nozzle a may be supplied from a suitable source of pressure, not shown. For convenience, air supply 35 may be used to energize fluid amplifier 41. A fluid signal or pulse applied to control port :1 of fluid amplifier 41 causes the power stream to switch to outlet passage c, or to remain there if the power stream was flowing through outlet passage c prior to the pulse. Likewise, a fluid signal or pulse applied to control port e causes the power stream to switch to outlet passage b.

The basic elements of variable capacitor 45 include a base 55 having a cylindrical chamber 50, and a piston 46 slideably positioned therein. Attached to base 55 is a bellows 48 which connects to piston 46 through a shaft 47. A vacuum signal is applied to the interior of bellows 48 through a port SI, as will hereinafter be explained. A spring 49 opposes the inward movement of bellows 48. The bellows assembly is covered by a pressure case 54, which is attached to base 55v A pair of ports 52 and 53 in base 55 communicate with chamber 50, which is the capacitance chamber.

Pulses from pulse generating means 30 are applied through conduit 34, a fluid resistor 56, and a conduit 57 to control port cl of fluid amplifier 41. Pulses are also applied to port 52 of variable capacitor 45 through conduit 34 and a conduit 58. Port 53 of variable capacitor 45 is connected to control port e of the amplifier. A positive pulse from pulse generating means 30 travels through conduit 34, resistor 56, and conduit 57 to control port if of amplifier 41, causing the power stream to switch to outlet passage c. The same pulse also travels through conduit 58 to capacitance chamber 50, initiating a pressure rise therein. The rate of pressure increase within chamber 50 is controlled by the volume of capacitance chamber 50 and the effective resistance of the charging path described in the preceding sentence. When piston 46 is in the position shown, the volume is large, the charging time of the capacitor is relatively long, and the pressure rise relatively is slow. When piston 46 is moved to the left, the charging time of the capaci tor decreases, and the rate of pressure rise increases. When the pressure in chamber 50, acting upon control port e, reaches sufficient magnitude, the power stream of amplifier 41 switches to outlet passage b. From the foregoing it will be appreciated that the length of time during which the power stream flows through outlet passage depends upon the position of piston 46 within chamber 50.

Fuel valve means 59 is provided for controlling the flow of fuel to the engine, according to signals received from pulse modifying means 40. Fuel valve means 59 comprises the following element. A housing 60 is mounted close to air intake passage 13. Inside housing 60, a diaphragm 61 and two parti tions of the housing define four chambers 62-65. A needle 66 is attached to diaphragm 61. Needle 66 passes through seal 68 and operates to open or close aperture 67, according to its vertical position which is controlled by the flexure of diaphragm 61. A spring 83 is provided in chamber 65 to nor mally hold diaphragm 61 and needle 66 upward to close aperture 67 in the absence of fluid signals. Fuel at a working pressure is supplied to chamber 62 through a port 69 from a fuel supply 70. Chamber 63 communicates through a port 71 to injector means 76, which is positioned within air intake passage 13.

Fuel valve means 59 is operated by fluid pulses from pulse modifying means 40 as follows. Pulses from outlet passages 12 and c of amplifier 41 are applied to chambers 65 and 64 offuel valve means 59 by

conduits

72 and 73, and

ports

74 and 75, respectively. An ON pulse from outlet passage c of the amplifier increases the pressure in chamber 64, thereby causing diaphragm 61 and needle 66 to move downward. This opens aperture 67, allowing fuel at a pressure from chamber 62 to flow through chamber 63 to injector means 76. Fuel exiting from injector means 76 is broken up to a fine spray for mixture with the air passing through air intake passage 13. A venturi tube 16 positioned within air intake passage 13 increases the velocity of the air in the locality of the injector means to aid in the mixture process. At the end of an ON pulse, the power stream of amplifier 41 is switched to pass through outlet passage 12 to pressurize chamber 65. This pushes diaphragm 61 and needle 66 upward to block aperture 67, thereby cutting offthe flow of fuel to injector means 76.

Engine manifold pressure is sensed at a manifold pressure lap 15, and is applied to port 51 of variable capacitor 45 by a conduit 78. Also connected to conduit 78 is a conduit 79 and a capillary tube 80, and a conduit 86 and a capillary tube 85, the operation of which is explained hereinafter.

When the engine is at idle, very little fuel is required. Under this condition throttle butterfly valve 14 is closed, the small air flow required enters air intake passage 13 through idle air passage 17, and manifold pressure is low, or, stated another way, manifold vacuum is high. This high manifold vacuum is supplied to the interior of bellows 48 of variable capacitor 45 through conduit 78 and port 51. Volume 81 is filled with a gas at normal sea level atmospheric pressure, and sealed by case 54. The force generated on the end of bellows 48 by the atmospheric pressure within case 54 and the high engine manifold vacuum inside bellows 48 causes the bellows to contract against spring 49, moving piston 46 to the left, greatly reducing the volume of chamber 50. With the volume of chamber 50 thus reduced, the duration of pulses passing through outlet passage c ofamplifier 41 to the fuel valve is also decreased, so that the duration of the fuel pulses injected by injector means 76 is at a minimum. It will be appreciated that the diameter of chamber 50 the length of shaft 47, and the stiffness of spring 49 are so chosen that the proper amount of fuel is supplied to the engine under idle, as well as other operating conditions.

When engine 10 is under heavy load, such as might be encountered during acceleration, throttle butterfly valve 14 is opened, allowing a great quantity of air to enter air intake passage 13. Accordingly, manifold pressure rises i.e., manifold vacuum decreases. With the decrease in manifold vacuum, the pressure force generated on the end of bellows 48 is no longer sufficient to overcome the force exerted by spring 49. Therefore bellows 47 expands, pulling shaft 47 and piston 46 to the right. This movement increases the volume of chamber 50, which in turn increases the duration of the fuel pulses applied to injector means 76.

For inten'nediate settings of throttle butterfly valve 14, manifold vacuum assumes an intermediate value, as does the position of piston 46. The quantity of fuel supplied per pulse is determined solely by the duration of the pulse, since fuel is supplied to the valve at a constant supply pressure. Thus, it will be appreciated that the fuel metering system of FIG. 1 is effective to automatically supply the proper amount of fuel to engine 10 through all ranges of engine speed and engine loadmg.

It is well known that in addition to metering fuel according to engine speed and load, it is desirable to adjust the quantity of fuel delivered according to engine temperature, ambient air temperature, and ambient air pressure. To effect these adjustments, compensation devices are provided in the fuel injection system of FIG. 1.

For example, when engine 10 is cold, such as during start-up and warm-up phases of operation, it is desirable to supply a fuel-air mixture that is richer than normal. Accordingly, temperature sensing means or means responsive to engine temperature 77 is provided. Temperature sensing means 77 includes capillary tube which is a very small diameter tube which is mounted on or near engine block 11. in another embodiment, capillary tube 80 is placed in a small well adjacent the exhaust manifold of the engine. Capillary tube 80 uses the dependence of the viscosity of air upon its temperature to provide a variable impedance to the flow of air therethrough. A conduit 82 connects from air cleaner 12 to capillary tube 80, and a conduit 79 connects from capillary tube 79 to conduit 78. Engine manifold vacuum in air intake passage 13 draws air through air cleaner 12, conduit 82, capillary 80 and conduit 79. Manifold pressure tap 15 acts as a pressure dropping resistance, since its diameter is smaller than the diameter of conduit 78. During normal running of the engine, the high temperature of engine block 11 heats the air in capillary tube 80 thereby increasing its viscosity to the point that very little air can flow through the series path of conduit 82, capillary tube 80, conduit 79, and manifold pressure tap 15. Consequently, air flow rate through manifold pressure tap 15 is negligible (There is no steady state air flow in conduit 78 since bellows 48 represents a closed volume.) Therefore, the pressure in conduit 78 is substantially the same as the pressure in air intake passage 13, and the fuel metering system operates substantially as described in the foregoing paragraphs.

However, when engine block 11 is cold, the lower viscosity of cool air permits some flow of air through capillary tube 80, conduit 79, and manifold pressure tap 15 into air intake passage 13. This air flow through manifold pressure tap 15 causes a pressure drop insuring that the pressure in conduit 78 will be somewhat higher than the pressure in intake passage 13, (i.e., the vacuum in conduit 78 will be somewhat lower than the vacuum in intake passage 13) no matter what position throttle butterfly valve 14 assumes, so long as engine block 11 is cold. A somewhat higher pressure in conduit 78 causes bellows 48 to expand, increasing the volume of chamber 50. This leads to the increase in the duration of the fuel pulses supplied, thereby providing an enriched mixture to the engine.

Similarly. means responsive to air temperature 84, which comprises capillary tube 85 and conduit 86 is provided for compensating for changes in ambient air temperature. Air is drawn through conduit 82, capillary tube 85, and conduit 86 which passes behind air intake passage 13) to join conduit 78. Capillary tube 85 is placed inside air intake passage 13 where it is exposed to the air drawn therethrough. Capillary tube 85 is effective to vary the duration of fuel pulses supplied to the engine in the same manner as capillary tube 80 previously described.

It is known that a percent reduction in fuel flow is needed at 10,000 feet altitude compared with the fuel flow required at sea level for a standard day. This reduction is required to reflect the lesser density of air at higher altitudes. In addition, there is a 30 percent loss in engine vacuum at 10,000 feet. A volume 81 which is hermetically sealed by case 54 and which is applied to the backside of bellows 48 will compensate for the engine vacuum loss and will automatically shorten the pulses when changing from sea level to 10,000 feet. Additionally, by proper selection of the composition of gas sealed within volume 81, changes in ambient air temperature may also be accounted for. If volume 81 is also used for air temperature compensation, means responsive to air temperature 84 may be deleted.

In FIG. 2 there is shown an alternate embodiment of applicants invention which features the use of alternate types of pulse generating means, pulse modifying means, and engine temperature and barometric pressure compensating means illustrated in FIG. I. It also features the use of multipoint fuel injectors, and separate acceleration and deceleration circuits. In FIG. 2, internal combustion engine 110 comprises an en gine block It], a crank shaft 119, an air intake passage 113, and an air cleaner 112. A throttle butterfly valve 114 is positioned inside air intake passage H3.

Pulse generating means 130 is provided for generating a train of fluid pulses. Pulse generating means 130 comprises a commutator 131 which is attached to a shaft 132. Shaft 132 is rotatably driven by crankshaft 119 via suitable gearing (not shown). For convenience, shaft 132 may be coextensive with the ignition distributor shaft of the engine. Commutator 131 has a slot 134 which extends through 180 of arc. A brush 133 is held in contact with commutator 131 by springs or other means (not shown). Brush I33 holds a conduit 135 in alignment with slot 134. Rotation of shaft 132 alternately opens and closes the end of conduit 135. This action, together with the operation of fluid amplifier 136, described below, produces the train of fluid pulses.

A bistable fluid amplifier 136, which is shown schematically, has a power noule a, a pair of outlet passages b and c, and a pair of control ports d and e. Conduit 135 connects to control port e, while control port dis vented to the atmosphere through fluid resistor 137. Fluid amplifier 136 along with the other fluid amplifiers of FIG. 2 are supplied with air at working pressure from air pump 120 which is driven by crank shaft 119. For clearity, the air conduits from pump 120 to the various fluid amplifiers have been omitted from the drawing. As the power stream flows through fluid amplifier 136 to outlet passage b or r: it entrains a certain amount of air from control ports d and e, pulling the entrained air on through the amplifier. If the air entrained from the control ports is not replaced by air-flow into the control ports from outside the amplifier, a low pressure condition can develop which may be sufiicient to pull the power stream from one outlet passage to the other. For example, when commutator I3] is in the position shown, air is able to enter control port e from the atmosphere through slot 134 and conduit 135 to replace the air depleted from control port e by entrainment. However, the influx of air to control port d is impeded by fluid resistance 137, and a low pressure condition is therefore maintained in control port d. The pressure differential thus produced by ambient air pressure at control port e and reduced air pressure at control port at causes the power stream to switch to outlet passage b. When shaft 132 and commutator 131 have rotated so that slot 134 is not aligned with conduit 135, the influx of air to control port 2 is prevented, thus putting the pressure therein to a lower value than the pressure existing in control port :1. This pressure dif ferential causes the power stream to switch to outlet passage c. Thus, there appears at outlet passage b of fluid amplifier 136, a train of fluid pulses having a frequency proportional to the speed of the engine.

Pulse modifying means 139 is provided for performing the same pulse duration modulation function performed by amplifier 41 and variable capacitor 45 of FIG. I, but by means of a different method of operation. Pulse modifying means 139 includes a fluid amplifier I40 and a variable capacitor I41. Fluid amplifier 140 is of the bistable or wall attachment type, and includes a power nozzle 0, a pair of outlet passages b and c and a pair of control ports d and e. Control port e communicates with capacitance chamber 142 of variable capacitor 141 via a conduit 143. The various components of variable capacitor 141 are shown more clearly in FIG. 3v

In FIG. 3, variable capacitor 141 comprises a housing 151 which defines two cylindrical chambers I42 and 152. A piston 144 in chamber 142 and a piston 145 in chamber 152 are connected by a shaft 146. A first spring 147 in chamber 152 positioned between housing 151 and piston 145 opposes the leftward movement thereof. A second, smaller spring 148 is also located in chamber 152 coaxial with shaft 146. The left end of spring 148 abuts against housing 151, and the right end of spring 148 engages a flange 153 of shaft 146 when piston 145 has moved a sufficient distance to the left. A pair of ports [49 and communicate with

chambers

142 and 152, respectively. Seals 154 on

pistons

144 and 145 give the pistons air tight fits in their respective chambers.

Referring again to FIG. 2, in the absence of a signal at control port :1, the power stream of fluid amplifier 140 will be biased to pass through outlet passage 0 because control port e communicates only with the closed volume of chamber 142. As explained above with reference to fluid amplifier 136, entrainment causes depletion of air from control port 2 resulting in a low pressure condition therein which is sufficient to switch the flow to outlet passage c. This condition represents the normally biased, no signal condition of fluid amplifier 140. Pulses from pulse generating means 130 are applied to control port doffluid amplifier 140 by conduit 138.

The operation of the modulator circuit comprising fluid amplifier 140 and variable capacitor 141 will now be described. A more detailed description may be found in patent application Ser. No. 851,238, now abandoned, by M. P. Miller filed Aug. 19, 1969 and assigned to the same assignee as the present application. A positive pressure pulse arriving at control port d ofamplifier 140 causes fluid to pass through control port e to charge capacitance chamber 142 to a relatively high pressure condition. The arrival of such a pulse at control port d does not cause a change in the output of the amplifier; the power stream continues to pass through outlet passage c. Upon termination of the positive pressure pulse at control port d, the following instantaneous conditions exist. The pressure in control port d is returned to a near ambient condition, the pressure in control port e and capacitance chamber 142 remains at the higher charged pressure. The pressure differential thus existing causes the power stream to switch to outlet passage b of fluid amplifier 140, and the high pressure fluid in capacitance chamber 142 begins to discharge through control port e, merging with the power stream, and passing through outlet passage 1). This condition continues until capacitance chamber 142 has completely discharged and the pressure therein begins to go below ambient due to entrainment through control port 2. The low pressure thus created biases the power stream, causing it to switch back to outlet passage 6. The length of time during which the power stream passes through outlet passage b is equal to the time required for capacitance chamber 142 to discharge. It will be appreciated that this discharge time is a function of the RC time constant of the discharge circuit, wherein the capacitance is determined by the volume of capacitance chamber 142, and

the resistance is the inherent resistance presented by control port e, determined principally by its diameter. In summary, pulse modifying means 139 functions as follows: the output of amplifier 140 is initially in outlet passage initiation of a pressure pulse at control port d causes no change in the output of amplifier 140; upon termination of the pulse applied to control port d, output flow of amplifier 140 switches to outlet passage b, and remains therein for a length of time determined by the volume of capacitance chamber 142; at the end of this time period, output flow of amplifier 140 returns to outlet passage c. The circuit is then ready for receipt of the next pulse, and the cycle is repeated. It will be appreciated that the circuit just described functions as a pulse width modulator.

The pulse width modulated fluid pulses from amplifier 140 are amplified by

amplifiers

155 and 156. Fluid amplifier 155 is a bistable summing amplifier comprising a power nozzle a, a pair of outlet passages b and c, a first control port pair d and e, and a second control port pair f and 3. Control port f is sealed by a plug 252, and signals are applied to control port 3 only during engine deceleration, as is described in a subsequent paragraph. Therefore. in normal operation, the output state of amplifier 155 is determined solely by the inputs applied to control ports d and e. Outlet passage b of amplifier 140 connects to control port d of amplifier 155 through a conduit 157. Similarly, outlet passage 0 of amplifier 140 connects to control port 2 of amplifier 155 through a conduit 158. Outlet passage 1: of amplifier 155 connects to control port d of amplifier 156 through conduit 159, and outlet passage c of amplifier 155 connects to control port e of amplifier 156 through a conduit 160. In normal operation, the output of amplifier 140 is amplified by amplifier Likewise, the output of amplifier 155 is amplified by amplifier 156, which is also a bistable fluid amplifier. The output of amplifier 156 is used to operate a primary fuel valve 200. Outlet passage b of amplifier 156 connects through a conduit 16] to a port 201 of primary fuel valve 200. Similarly, outlet passage 0 of amplifier 156 connects through a conduit 162 to a port 202 of the primary fuel valve.

In addition to the fluid pulses applied to

ports

201 and 202 by fluid amplifier 156, two other inputs are applied to primary fuel valve 200. They are: fuel supplied to port 204, and engine manifold vacuum applied to port 203. Fuel from a fuel tank 290 is delivered to a port 204 of primary fuel valve 200 by an electric fuel pump 29], and a conduit 293. The fuel pressure in conduit 293 is held constant by a pressure regulator 292, which allows excess fuel to return to tank 290 through a bypass conduit 294. Manifold vacuum is applied to port 203 of primary fuel valve 200 by a conduit, 167 which connects to a tap 116 in air intake passage 113.

Primary fuel valve 200 is shown in cross sectional view in F16. 4. The housing for primary fuel valve 200 comprises four sections, 206 through 209, which are fastened together by means, not shown. A diaphragm 210 is positioned between section 206 and section 207v Similarly, a diaphragm 211 is positioned between

sections

207 and 208, and a diaphragm 212 is positioned between

sections

208 and 209. A chamber 223 is formed with sections 206, and is bounded on the lower side by diaphragm 210. A port 203 communicates with chamber 223. A chamber 224 is formed within section 207, and is bounded on the top by diaphragm 210 and on the bottom by diaphragm 211. A port 202 communicates with chamber 224. In a similar manner, a chamber 225 is formed within section 208. Chamber 225 is bounded on the top by diaphragm 211, and on the bottom by diaphragm 212. A port 201 communicates with chamber 225. A chamber 226 is formed with sections 209, and is bounded on the top by diaphragm 212. A port 204 communicates with chamber 226.

A button 217 is attached to the bottom of diaphragm 212 for movement therewith. Protruding upward from the floor of chamber 226, and aligned with button 217, is pedestal 218. Inside pedestal 218 is a plurality of passages 219, which connect to ports 205. In general, primary fuel valve 200 should have one passage 219 and one port 205 per engine cylinder. Fuel at a working pressure supplied to port 204 enters chamber 226.

1n the absence of a downward force acting upon diaphragm 212, the fuel pressure within chamber 226 forces diaphragm 212 and button 217 upward, allowing fuel to pass through passages 219 to ports 205. When a downward force is applied to diaphragm 212, as is explained below, button 217 is held against pedestal 218, and fuel is prevented from passing into passages 219 to ports 205. Thus it will be appreciated that the flexure of diaphragm 212 is effective to control the flow of fuel to ports 205.

A pair of discs, 213 and 215, is attached to the bottom sides of

diaphragms

210 and 211, respectively. A pair of spools, 214- and 216 is attached to

discs

213 and 215, respectively, in alignment with button 217 and pedestal 218, A sleeve 227 is provided in section 206. A spring 220 and a slug 222 are provided within sleeve 227. Spring 220 urges slug 222 downward onto diaphragm 210. This force is transmitted through

spool

217 and 216 to diaphragm 212. The amount of force exerted by spring 220 may be controlled by a thumb screw 221, and is normally set so that in the absence of control signals, the force exerted by spring 220 is sufficient to overcome the fuel pressure within chamber 226, so as to hold button 217 against pedestal 218. In this condition, primary fuel valve 200 is said to be OFF.

Primary fuel valve 200 operates as follows. When engine in FIG. 2 is OFF, spring 220 keeps primary fuel valve 200 in an OFF condition. When engine 110 is tuning, manifold vacuum applied via port 203 to chamber 223 draws diaphragm 210 upward, overcoming the force exerted by spring 220. The flow of fuel through the valve is then controlled by diaphragm 211 which may move spool 216 up and down against diaphragm 212, according to the pressures in

chambers

224 and 225. The pulse width modulated fluid pulses from pulse modifying means 139 are applied to

ports

201 and 202 of primary fuel valve 200, as previously described. During an 0N pulse, the power stream of fluid amplifier 156 flows through outlet passage b, conduit 161, and port 201 to pressurize chamber 225. At the same time, a relatively low pressure condition exists in outlet passage c at amplifier 156 and chamber 224 of primary fuel valve 200. This pressure differential causes diaphragm 211 to move upward, allowing the fuel pressure within chamber 226 to push diaphragm 212 upward, which permits fuel to pass through passages 219 to ports 205. At the end of an ON pulse, the power stream of fluid amplifier 156 switches to outlet passage 0, thereby pressurizing chamber 224. The high pressure in chamber 224 pushes diaphragm 211 downward, thereby turning OFF the fuel valve.

Fuel pulses are thus delivered to ports 205 of primary fuel valve 200 and are transmitted through a conduit 168 to in jeetor means 169. In this embodiment, injector means 169 comprises an inner nozzle 170, and a larger coaxial nozzle 171. The two nozzles are mounted in air intake passage 113 near engine intake valve 118. Fuel pulses are supplied to the inner nozzle 170, where they are broken up into a fine spray for mixture with the air in intake passage 113. Air from air cleaner 112 is supplied through a conduit 172 to the larger nozzle 171. Manifold vacuum in air intake passage 113 draws air inward through conduit 172 and nozzle 171. This flow of air past nozzle 170 helps atomize the fuel pulse to form a uniform mixture. Also, the air passing through nozzle 171 maintains the pressure surrounding nozzle 170 at near ambient, thus insuring uniform performance of fuel injector 170 regardless of engine manifold pressure. The embodiment of applicants invention shown in FIG. 2 will also work, of course, with conventional spring check valve fuel injectors.

Likewise, it is possible, and in some cases might be advantageous, to use conventional electrical solenoid injectors with applicants invention. For example, the embodiment shown in F IG. 2 could easily be so adapted by replacing in jec tor means 169 and primary fuel valve 200 by a conventional electrical solenoid injector, which includes both valve means and injector means. The fluid signals at

conduits

161 and 162 could be used to energize the solenoid by means of a conventional fluidic-to-electrical interface. Fuel from conduit 293 would be supplied directly to the electrical solenoid injectors.

Referring now to FIG. 5, the overall performance of the fuel system of FIG. 2 is shown for difierent steady state operating conditions. The vertical scale of the graph of FIG. 5 represents the rate of fuel delivery to the engine, with higher fuel rates towards the tope of the graph. The horizontal scale represents manifold vacuum, with increasing vacuum towards the right of the graph. In the graph there is shown a family of fuel flow curves for different engine speeds at standard sea level conditions. The lower curve shows fuel flow rate versus manifold pressure for a constant engine speed of 600 RPM. The next curve shows the fuel metering characteristics of this system for an engine speed of 1,000 RPM, and so on up to the top curve which represents characteristics at an engine speed of 5,000 RPM. It will be noted that, for a given manifold vacuum, fuel delivery rate increases with engine speed. This result follows from the fact that for a given manifold vacuum, pulse duration {determined by the position of piston 144 in variable capacitor 141) remains constant, and the frequency or repetition rate of pulses from pulse generating means 130 varies according to engine speed. It should be noted also that for a given engine speed, lower manifold vacuum, which corresponds to a wider open throttle setting, results in an increased fuel delivery rate.

For each of the curves of FIG. 5, there is a change of slope at a break point which corresponds to a certain value of manifold vacuum. This change of slope provides for economizer" fuel delivery, wherein a somewhat leaner mixture is provided at low throttle settings (high manifold vacuum) for better economy during cruising and a somewhat richer mixture is provided at high throttle settings for better power during acceleration or high speed operation. One model of the system of FIG. 2 which was tested on a particular engine was found to give best results when the break point was set at a manifold vacuum of 5 inches of mercury. The change in slope at the break point is provided by spring 148 (FIG. 3). As piston 145 of variable capacitor 141 moves to the left under the influence of increasing manifold vacuum, it is opposed by spring 147 having a given stiffness. But after piston 145 has moved far enough for spring 148 to engage flange I53, further leftward movement is then opposed by the combined stiffness of

springs

147 and 148. The result is that before spring 148 is engaged, a given increment of manifold vacuum applied to port [50 produces a relatively greater decrease in the volume of chamber 142 and the same increment would after spring 148 is engaged.

In addition to the steady state operation of the fuel injection system of FIG. 2, explained in the preceding paragraphs, additional modes of operation are provided for use during acceleration, deceleration, cold engine operation, and change of altitude.

Referring again to FIG. 2, a temperature sensing means or means responsive to engine temperature 174 is provided for applying compensations to conduit 166, which delivers the controlling vacuum signal to variable capacitor 141. A thermostat 175 is mounted on or near engine block 111 for response according to the temperature of the engine. Thermostat 175 acts through a link 178 to operate a lever 176, which is pivoted at a fulcrum 177. A nozzle [79, which is positioned near the end of lever 176, communicates with conduit 166 through a conduit 180 and a resistor 181. When the engine is at normal operating temperature, the end of lever 176 is held against nozzle I79, effectively closing it. In this condition, temperature sensing means 174 has no effect, and the operation of the fuel injector systems is as previously described. When the engine is at low temperature, thermostat I75 swings lever 176 away from nozzle 179, allowing air to bleed into nozzle 179, through resistor 181, through conduit 180, resistor 165, conduit 164, and tap 117 to air intake passage 113. The difference in pressure between ambient and the pressure within intake passage 113 is dropped across

resistors

181 and 165.

Conduits

180 and 166 are held at an intermediate pressure which is slightly higher than manifold pressure, thereby causing piston 144 of variable capacitor 141 to move towards the right. This movement gives a wider pulse output, and hence a richer mixture. After engine has warmed up, thermostat closes nozzle 179, and temperature sensing means 174 exerts no further influence on the operation of the fuel system. Temperature sensing means 174 thus acts as a variable impedance, and allows a quantity of air to enter conduit according to engine temperature.

Altitude compensating means or means responsive to engine temperature, 182 is also provided for applying compensations to conduit 166. In the embodiment shown in FIG. 2, altitude compensating means 182 comprises a bellows control valve which comprises a bellows 183, a needle 184, and an orifice 18$. Bellows 183 is an aneroid type element, sealed at a certain pressure so as to expand at higher altitudes and contract at lower altitudes. Needle 184 is tapered to fit into orifice 185 to provide a variable impedance to the flow of fluid therethrough. Altitude compensating means 182 is calibrated so that orifice 185 is completely blocked at an ambient air pressure corresponding to l0,000 feet altitude, and fully open at sea level. As previously described, piston 145 of variable capacitor 141 assumes a position according to the balance of forces exerted upon it by spring 147, the vacuum signal applied through port 150, and ambient air pressure on the back side of piston 145. As an automobile travels from sea level to 10,000 feet altitude, the manifold vacuum, i.e., the difference between air intake passage pressure and ambient air pressure, decreases. However, since the spring force in the variable capacitor does not change with altitude, were it not for altitude compensating means 182, the effect of the reduced manifold vacuum would be for piston 145 to move to the right, thereby increasing pulse duration and enrichening the mixture. It is therefore necessary to compensate the circuit to prevent enrichment of mixture at high altitudes. Further, it is desirable to over compensate the circuit so as to provide a 10 percent reduction in fuel delivered because of the reduced air density at higher altitudes. These compensations are provided by altitude compensating means 182 as follows. At sea level, air enters orifice 185, flows through conduit 180, resistor I65, conduit 164 and tap 117 to air intake passage 113. The pressure drop of air flowing through resistor I65 insures that the pressure in

conduit

180 and 166 will be somewhat higher than the pressure in conduit 164. Stated another way, the vacuum signal applied to the variable capacitor 141 is less than actual manifold vacuum in conduit 164. The entire fuel system is then calibrated to give proper fuel delivery at sea level with this reduced vacuum in conduit 166. As ambient air pressure gradually decreases until a pressure equivalent to 10,000 feet is reached, needle I84 moves progressively into orifice 185, completely blocking it at an altitude of l0,000 feet. Correspondingly, the amount of air flow through the circuit of orifice 185, conduit 180, resistor 165 and eventually into air intake passage 113 is progressively reduced, so that the pressure drop across resistor 16$ diminishes to zero at l0,000 feet (not counting any pressure drop due to the engine temperature compensation circuit, which operates in addition, but independently of the altitude compensation circuit). With orifice 185 closed, the pressure in conduit 166 is the same as the pressure in conduit 164, which is the same as the pressure in air intake passage 113. It is seen therefore, that although engine manifold vacuum tends to decrease at higher altitudes, this effect is compensated for, and the control vacuum actually delivered to the pulse width modulator through conduit 166 is adjusted, so as to compensate for this decrease in manifold pressure, and to provide for the desired 10 percent decrease in engine fuel requirements at 10,000 feet altitude.

It will be appreciated that the altitude and temperature corrections and compensations applied to the vacuum signal which operates the pulse width modulator operate in addition to but substantially independent of one another and the engine manifold vacuum. For given engine temperature and altitude conditioning, the fuel injection system of FIG. 2 continues to operate primarily according to manifold vacuum, as previously described.

Air temperature compensating means may be connnected to conduit 166, as in the embodiment of FIG. 1, if, for a particular engine, it is found desirable to do so.

Acceleration performance of internal combustion engines may be improved by supplying to the engine during acceleration a greater quantity of fuel than is normally required. Accordingly, acceleration mode fuel valve 300 is provided, the details of which are shown in FIG. 6. Housing for fuel valve 300 comprises

sections

306, 307 and 309. Inside the housing are

chambers

323 and 324, which are separated by a diaphragm 310. A disc 313 is attached to the bottom of diaphragm 310, and a spool 314 is attached to the bottom of disc 313. Section 309 of fuel valve 300 is substantially identical to section 209 of fuel 200, in FIG. 4. The important elements of the bottom section of fuel valve 300 are a diaphragm 312, a button 317, a pedestal 318, passages 319, ports 305 and port 304. Button 317 is normally held down on pedestal 318 by a spring 320, which urges a slug 322 downward on diaphragm 310.

Referring agin to FIG. 2, fuel is supplied to port 304 of acceleration mode fuel valve 300 from conduit 293, which carries fuel at the working pressure. Manifold vacuum is applied to port 301 by tap 116 and conduit 167. During steady state operation of the engine, manifold pressure is constant at some value, and the pressures in

chambers

323 and 324 equalize through a port 302, in diaphragm 310. With no pressure differential acting on diaphragm 310, spring 320 holds button 317 against pedestal 318, preventing the delivery of fuel to ports 305. During heavy accelerations, throttle butterfly 114 is opened quickly, and there is a sudden increase in manifold pressure. This sudden rise in manifold pressure creates a mo mentary pressure differential across diaphragm 310, flexing it upward thereby allowing fuel to pass through passages 319 to ports 305. As this is taking place, the pressure in

chambers

323 and 324 is being equalized by flow through port 302. When the pressure difference becomes small enough, spring 320 once again forces button 317 downward, cutting 011' the flow of fuel. The length of time during which acceleration fuel flows depends upon the volume of

chambers

323 and 324, the diameter of port 302, and the force exerted by spring 320, which may be adjusted by a thumb screw 321. Fuel from port 305 is delivered to conduit 169 and thence to injector means 169. It will be appreciated from the foregoing that acceleration mode fuel valve 300 delivers fuel to the engine during accelerations, in amounts according to the suddenness and degree of the acceleration, independently of the normal fuel delivery.

It is desirable in automobile engines to provide means for cutting off the fuel during decelerations, so as to improve the braking efi'ect on the engine. Accordingly, the fuel injection system of F 10. 2 is provided with fuel cutoff means 250 which is operable to cut 011" the fuel whenever the engine throttle is closed and engine speed exceeds a predetermined value. Pressure pulses from outlet passage of amplifier 136 are conducted by a conduit 188 to control port d of a bistable fluid amplifier 186. These pressure pulses are identical to the pressure pulses conveyed by conduit 138 (except for a 180 phase reversal). A fluidic capacitor 189 is connected to control port e of amplifier 186. This circuit arrangement is identical to the circuit of fluid amplifier 140 and variable capacitor 141, except for the fact that fluid capacitor 189 is fixed in value, so that pulses passing out outlet passage b of amplifier 186 are all of uniform width. These pulses are filtered by a capacitor 190, to form an analog pressure level therein. The magnitude of pressure existing in capacitor 190 depends solely upon the frequency of the received pulses, and hence upon engine speed, since the widths of pulses delivered to capacitor 190 are fixed. The pressure in capacitor 190 is delivered to control port d of a bistable fluid amplifier 187 through a conduit 191, a resistor 192 and a valve 193. Valve 193 is a conventional bellows activated valve operable to open or close the fluid path from resistor 192 to control port d of fluid amplifier 187 according to signals applied to the bellows via a conduit 194. Valve 193 is so configured that application of vacuum to conduit 194 closes the fluid path through the valve, while ambient pressure in conduit 194 allows valve 193 to open.

The vacuum signal applied to conduit 194 originates at a tap 115, and is indicative of the position of throttle butterfly valve 1 14. When throttle butterfly valve 114 is open anywhere from a slight amount to full open, port 115 is in effect downstream from the throttle, and is subject to manifold pressure, which is always less than ambient pressure. When throttle butterfly 114 is closed, tap 115 is effectively upstream thereof, and as such is subject to near ambient pressure. Thus the pressure at tap 115 and conduit 194 undergoes a sharp transition from near ambient pressure to relatively large manifold vacuum upon opening of the engine throttle.

Fluid passing through outlet passage c of amplifier 186 is received and filtered by a capacitor 195. This flow of fluid represents the remaining output of amplifier 186 other than the uniform pulses, which are supplied to capacitor 190. Preferably, the volume of capacitor 189 is adjusted so that capacitor 195 receives more than half and capacitor 190 receives less than half of the time averaged output of amplifier 186, when the engine is operating at maximum speed. This insures that sufficient pressure will be maintained in capacitor 195 to operate a fluid amplifier 187. Fluid from capacitor 195 is supplied to power nozzle a of amplifier 187 from conduit 196, and to control port e of amplifier 187 through a conduit 197 and a resistor 198. Outlet passage c of amplifier 187 is vented to the atmosphere, an outlet passage 1: is connected to the control bellows of a valve 199, which is similar to valve 193 except that valve 189 is closed when its bellows is pressurized, and opened when its bellows is subject to ambient air pressure. Air at a working pressure is supplied to a port 253 from air pump 120, by conduit means not shown. Valve 199 functions to control the flow of air from port 253 through a conduit 251 to control port e of amplifier 155. Control port f of amplifier is sealed by plug 252.

In normal engine operation, pressure applied to control port e of amplifier 187 biases the power stream to flow through outlet passage b to valve 199, holding it closed. In that condition, both control ports f and g of amplifier 155 are blocked, and have no effect on the operation of the amplifierv When throttle butterfly valve 114 is closed, ambient pressure at tap 115 and conduit 194 allow valve 193 to open, thereby allow ing fluid from capacitor 190 to flow into control port b of amplifier 187. However, unless the engine is operating at a speed above a predetermined value, the pressure delivered to control port d through resistor 192 from capacitor 190 is insuffcient to overcome the bias applied to control port d to resistor 198. This prevents fuel from being cut ofl'during engine idling condition. However, if the throttle is closed and engine speed is above a certain value such as occurs during deceleration, valve 193 is open, and the pressure in control port of causes the power stream of amplifier 187 to switch to outlet passage c. The removal of pressure to the bellows of valve 199 allows the valve to open, and pressure from port 250 is applied to control port 8 amplifier 155. This signal at control port g is of suffcient magnitude to override the normal fuel pulse signals in control port d, and the fuel is effectively cut off, until the throttle is reopened, or until engine speed drops below the predetermined value.

1 claim as my invention:

1. A fuel system for an internal combustion engine having an air intake passage, comprising:

pulse generating means for generating a train of fluid pulses whose frequency is indicative of engine speed;

conduit means in communication with said air intake passage;

fluid resistance means connected between said conduit means and said air intake passage;

variable impedance means connected to said conduit means, said variable impedance means operable to admit a quantity of air into said conduit means according to parameters associated with the operation of the engine; pulse modifying means in communication with said pulse generating means and said conduit means, said pulse modifying means for varying the duration of said fluid pulses according to pressure in said conduit means;

fuel valve means connected to said pulse modifying means for energization upon occurrence of a fluid pulse for the duration thereof; and

injector means operatively connected to said fuel valve means, said injector means adapted for supplying fuel to the engine upon energization of said fuel valve means.

2v Apparatus according to claim I wherein said variable impedance means comprises means responsive to engine temperature.

3. Apparatus according to claim I wherein said variable impedance means comprises means responsive to atmospheric pressure.

4. Apparatus according to claim 1 wherein said variable impedance means comprises means responsive to air temperature.

5. The apparatus of claim 1 further including fuel cutoff means connected to said pulse generating means and said air intake passage for producing fuel cutoff signals whenever a low pressure condition exists in said air intake passage and the frequency of said train of fluid pulses exceeds a predetermined value, said fuel cutoff means further connected to said pulse modifying means for supplying said fuel cutoff signals thereto, and wherein said pulse modifying means is adapted to prevent the flow of fuel to the engine when said fuel cutoff signals are received.

6. Apparatus according to claim 5 wherein said fuel cutoff means includes fluid amplifier means.

7. The apparatus of claim I wherein said internal combustion engine includes throttle means, and further including fuel cutoff means connected to said pulse generating means and said throttle means for producing fuel cutofi" signals whenever said throttle means is closed and the frequency of said train of fluid pulses exceeds a predetermined value, said fuel cutofi means further connected to said pulse modifying means for supplying said fuel cutoff signals thereto, and wherein said pulse modifying means is adapted to prevent the flow of fuel to the engine when said fuel cutoffsignals are received.

Claims

1. A fuel system for an internal combustion engine having an air intake passage, comprising: pulse generating means for generating a train of fluid pulses whose frequency is indicative of engine speed; conduit means in communication with said air intake passage; fluid resistance means connected between said conduit means and said air intake passage; variable impedance means connected to said conduit means, said variable impedance means operable to admit a quantity of air into said conduit means according to parameters associated with the operation of the engine; pulse modifying means in communication with said pulse generating means and said conduit means, said pulse modifying means for varying the duration of said fluid pulses according to pressure in said conduit means; fuel valve means connected to said pulse modifying means for energization upon occurrence of a fluid pulse for the duration thereof; and injector means operatively connected to said fuel valve means, said injector means adapted for supplying fuel to the engine upon energization of said fuel valve means.

2. Apparatus according to claim 1 wherein said variable impedance means comprises means responsive to engine temperature.

3. Apparatus according to claim 1 wherein said variable impedance means comprises means responsive to atmospheric pressure.

7. The apparatus of claim 1 wherein said internal combustion engine includes throttle means, and further including fuel cutoff means connected to said pulse generating means and said throttle means for producing fuel cutoff signals whenever said throttle means is closed and the frequency of said train of fluid pulses exceeds a predetermined value, said fuel cutoff means further connected to said pulse modifying means for supplying said fuel cutoff signals thereto, and wherein said pulse modifying means is adapted to prevent the flow of fuel to the engine when said fuel cutoff signals are received.