EP0200063B1

EP0200063B1 - Fuel injection system

Info

Publication number: EP0200063B1
Application number: EP19860105077
Authority: EP
Inventors: Michael D. Leshner; Ernest W. Chesnutis, Jr.
Original assignee: Bowles Fluidics Corp
Current assignee: Bowles Fluidics Corp
Priority date: 1985-04-30
Filing date: 1986-04-14
Publication date: 1990-01-17
Also published as: JPH0759920B2; AU625562B2; DE3668357D1; AU4367189A; EP0200063A1; CA1274130A; BR8601924A; AU5646786A; JPS627953A; AU589417B2

Description

This application is related to the application of Ronald D. Stouffer, WO-A-84/03335 and entitled "Improved Fluidic Transducer for Switching Fluid Flow", assigned to the assignee hereof.

Background and brief description of the invention

In fuel management systems for internal combustion engines, on-board computers are currently supplied with data from sensors monitoring various engine operating parameters, such as rpm, temperature, exhaust gas characteristics, mass air flow through the air intake manifold, accelerator pedal position, etc., to determine the proper fuel-air ratio for fuel economy.
Smoothness of engine operations and compliance with emission standards. The electrical control signals are supplied to a solenoid controlled fuel injection valve which typically is biased closed by a spring so that a large electrical current is required to open the valve. In this example, while modern electronic computers and microprocessors have been developed to provide highly accurate control siganls for controlling liquid flow, the control devices per se have typically been a solenoid controlled mechanical valve which have difficulty in accurately tracking electrical signals and delivering short liquid pulses mainly because of their large pintle mass which is magnified in the case of springs biasing them closed. The leading edge in particular of the liquid pulse delivered to the utilization system is not sharp. In the case of solenoid controlled fuel injectors for internal combustion engines, the output nozzles are very sensitive to fluid loading so that if a passageway to direct the output fuel pulse to a specific port intake target were attached, the performance is severely degraded. Reference is made to the article entitled "Electronic Fuel Injection" by Randolph, October 1984, Popular Science, pages 73-75; Automotive Engineering, October 1983, pages 40-45 and the pamphlet "High Technology from Buick", "the 3.8 SF Turbo".
Significant improvements in such systems have been provided in the above-identified related application of R. D. Stouffer wherein a bistable fluidic switch element with a cross-over type interaction chamber leading to a common outlet and to a pair of output passageways, one of the output passageways leading to the engine and the other leading to the supply tank. The bistable switch was reliably switched using a pair of control ports which had control tubes coupled thereto and shaken in prescribed manner by a solenoid which, in turn, was controlled by the on- board computer or microprocessor. In the Stouffer system, individual fuel return from each injector provides for "flushing" of fuel vapor bubbles which might enter the fuel inlet. The conventional system described earlier herein (and described more fully hereafter) has no means for flushing out a vapor bubble once it has entered the inlet. This feature allows the bistable fluidic switch system to use a lower system fuel pressure (on the high pressure rail). Current systems (such as those marketed by Robert Bosch) use approximately 27 to 37 psi (1 psi=0,07 bar=7000 Pa), to avoid the formation of vapor bubbles. Lower pressure systems require less complexity and less expensive pump.
An object of the present invention is to provide an improved fuel injection system of the type disclosed in the above-referenced Stouffer application. A further object of the invention is to provide improvements in fuel injection systems generally, particularly with respect to method and apparatus for improving the engine performance thereof.
The invention is defined in the accompanying Claim 1 and incorporates a bistable fluidic switch in a fuel injection system for an internal combustion engine.
According to one major feature in the claim, a flow control pin is projected into and out of an intrusion position in a flow path in a power nozzle of said fluidic switch in a region on one side of a centre line through said power nozzle and upstream of a throat thereof, to switch the state of said bistable switch and so change the flow of fuel from one to the other of the two output channels of the bistable fluidic switch.
By this means the use of side channels or control ports is eliminated and the fuel switching is accomplished solely by the interposition of a pin in the power nozzle thus simplifying the construction of the fluidic itself, eliminating small flow passages and the like and, at the same time, improving the response time, since there is no flow of fluid inside channels or delay involved in such flow.
In a preferred embodiment the axis of said power nozzle is at an angle relative to the axis of a chamber of the bistable fluidic switch so that in the absence of the flow control pin, the switch is in one predetermined state and is switched from that state to the other state by pin intrusion and always returns to that predetermined state on removal of the intrusion pin.
A second major feature of the invention is that air is supplied to each injector at a point in the output flow passage leading to the engine so as to pre-air atomize the fuel before injection of same into the air intake manifold on the engine. This has the following advantages:

A. It makes the flow calibration insensitive to changes in manifold vacuum-thereby eliminating the need to compensate the supply pressure for changes in manifold vacuum.
B. It improves the quality of the fuel/air spray which is of primary importance in fuel/air mixture preparation. Improved spray (smaller droplets) and distribution in the air stream flowing in the air intake manifold results in a greater degree of fuel vaporization, yielding more complete combustion. The improvements is manifested by smoother engine idle and substantial minimization of "idle shake".
C. For improved cold/warm-up operation, air supplied to the injectors may be selectively preheated, to improve early fuel vaporization characteristics. This technique is more effective than heating 100 percent of the combustion air during the first few minutes after a cold start (when very little heat is available). Thus, improved warm-up exhaust emissions will result.
D. Air supplied directly to the injectors is accounted for by the engine control computer. When the air flow is computed based on the manifold absolute pressure, the injector air is accounted for by its effect on manifold pressure. In a fuel metering system which makes use of direct air mass flow measurement, the source of injector air is downstream of the mass flow sensor. In either case, the source of injector air is derived from a source downstream of the combustion air filter.
E. The injector air flows in proportion to the manifold vacuum (atmospheric pressure minus manifold absolute pressure), producing the best spray (smallest droplet size) under the idle and light load conditions, when the vacuum is high-(15-20 in.hg.; 50,796-67,728 Pa) and coincidentally, the engine combustion is most sensitive to droplet size at idle and light load conditions.
F. Finally, the pin has a low mass. The low mass electromechanical actuator allows the injector to turn on and off with less delay than conventional injectors. This results in a flow calibration which maintains its linearity at pulse widths below 2 msec.
G. The introduction of air isolates the high vacuum condition of the engine from the fluidic element. Air enters the engine output leg of the fluidic element so that particular point does not see the vacuum of the intake manifold. There is not enough air added to greatly effect engine vacuum. The power nozzle then becomes the major source of pressure drop of the fluid in the system.

In view of the above mentioned use of a pin in the flow path of a fluidic element to cause switching of a fluid to one or the other of two outlets, the following two prior art documents are of interest:
US-A-3 906 979 discloses a transducer having a fluidic amplifier in which a fluid beam is passed via a nozzle into a chamber. At the outlet end of the chamber are two outlet ports divided from each other by a pointed projection extending towards said chamber. In the chamber, close to the outlet ports, is a pin and this pin, in a central position, extends through an axis extending along said nozzle at one end of the chamber and said pointed projection at the other end of the chamber. The pin is adapted to swing to one side or the other of said axis in order to change said fluid beam from one outlet port to the other. To effect this the pin is mounted on a pivoted frame carrying a coil and connecting leads. In operation signals are sent to the coil via said connecting leads to produce a flux that reacts with a stationary permanent magnet to cause said frame to pivot and thus to cause the pin to move to one side of the other of said axis. In this construction the pivoted frame, the coil carried by the frame and the connecting leads secured to the moving mass all contribute to the inertia of the device in response to the electrical signals.
In the second prior art, namely US-A-3 993 101, by the same applicants as in US-A-3 906 979, a tristable fluidic device is disclosed in which a movable deflector in the form of a pin can be moved from side-to-side across a flow path into which a central wall extends. In its non-displaced setting the pin is in a through-slot in the central wall thus leaving the flow paths on each side of the wall free. The pin is mounted on an electromagnetic device having electrical connections in order to supply currents of opposite polarity to the armature of the electromagnet. Thus, depending upon the polarity of the current the pin can be moved into one or the other of the flow paths on each side of the central wall. Here again the mass of the moving parts of the electromagnetic device contribute to the inertia of the device in response to electric signals.

Brief description of the drawings

The above and other objects, advantages and features of the invention will become more apparent when considered with the following specification and accompanying drawings wherein:

Fig. 1 is an enlarged plan silhouette view of an actual operating unit with exemplary dimensions thereon.
Fig. 2a is an enlarged plan silhouette view of an actual operating unit with exemplary dimensions thereon.
Fig. 2b is a silhouette of Fig. 2 showing the flow path with the pin in its intruding or projecting position in a flow path in the power nozzle.
Fig. 2c shows the flow paths with the pin in its unintruding or retracted position.
Fig. 3 is a schematic block diagram of a prior art (Bosch) fuel injection system which is currently commercially available.
Fig. 4 is a fuel injection system incorporating the invention.

Detailed description of the invention

Referring now to Figs. 1 and 2, the bistable fluidic switch 10 includes a body member 11 with a power nozzle 12 issuing fluid into chamber 13 formed with sidewalls 14 and 15 which diverge relative to the power nozzle and converge relative to common outlet 16 leading to a first output passage 17 which conveys fuel to the engine and a second output passage 18 which conveys unused fuel to a return rail to the supply or tank. The bistable fluidic switch 10 has the exemplary silhouette shown in Fig. 2 and the flow paths which will be described more fully hereafter.
Switch control pin or pintle 19 is moved through the transverse bore hole 20 by electromagnetic coil 21 which receives control signals from conventional on-board computer 22 which, in turn, receives a plurality of engine and performance data parameter signals on its input lines 23 from the various engine sensors and signal transducers (not shown). A spring 24 biases the pintle or pin and its driving armature to a neutral or non-intruding position. Passage 26 supplies air from the air intake to air atomized fuel in outlet passage 17 and isolates the fluidic from the vacuum thus making the flow calibration insensitive to changes in manifold vacuum thereby eliminating the need to compensate the supply pressure for changes in manifold vacuum. It also improves the quality of fuel spray which is of primary importance in fuel/ air mixture preparation. The improved spray results in smaller droplets to produce a greater degree of vaporization and hence, more complete combustion. This improvement is manifested by smoother engine idle. For improved cold/warm-up operation, air supplied to the injectors may be selectively preheated to improve early evaporation characteristics. Since this relatively low volume of air is supplied to each of the injectors, it can be heated using electric heater thermostatically controlled (not shown) in air rail line 98. This technique is more effective than heating 100 percent of the combustion air during the first few minutes after a cold start. It also results in improved warm-up exhaust emissions. That is, the emissions are reduced.
Moreover, the air supplied directly to the injectors is accounted for by the engine control computer 22. When the airflow is computed based on manifold absolute pressure, the injector is accounted for by its effect on manifold pressure. In a fuel metering system which makes use of direct air mass flow measurement, the source of inject air is downstream of the mass air flow sensor and of the combustion air filter. Finally, the injector air flow is in proportion to the manifold vacuum (atmospheric pressure minus manifold absolute pressure) thus producing the best spray pattern (smallest droplet size) under idle and light load conditions, when the vacuum is high (15-20 in.hg.; 50,796-67,728 Pa). Coincidentally, the engine combustion is most sensitive to droplet size at idle and light load conditions.
The pintle or pin 19 is of very low mass. Thus, this low mass electromechanical actuator allows the injector to turn on and off with less delay than conventional Bosch type injector. This results in a flow calibration which maintains its linearity at pulse widths below 2 msec.
A cover 9 seals the bistable switch, the passages to the power nozzle 12, return fuel passages and fuel to engine passage are all sealed and secured to body member 11 for, in this embodiment, direct substitution in a conventional multi-point fuel injection. The air input 26 is connected to air rail 98 by short pipe section 99.
As shown in Fig. 2b, when the pin 19 is in an intruding position, it is specifically located in a region to the right of the center line through the power nozzle 12 and upstream of the throat 12T of the power nozzle a short predetermined distance. It is essentially within this sector that the pin is most effective in effecting a switch. The design of the fluidic is such that in the normal case with the pin in non-intruding position the axis of the power nozzle 12 is canted about 8 degrees relative to the axis of chamber 13 so that the fuel will flow through passage 18 and return to the tank (as shown in Fig. 2c). When the pin intrudes in the flow pass in the power nozzle, it will cause a deflection of the jet of 15 to 16 degrees. The chamber effectively amplifies this deflection to cause the jet to travel along wall 15 and pass through common outlet 16 and be directed into outlet passage 17 leading to the engine, as shown in Fig. 2b.
As noted above, the bistable fluidic switch element has a chamber of the type wherein the sidewalls converge to a common outlet 16. The common outlet 16 with its converging sidewalls 13C and 14C isolate this chamber from the output channels 17 and 18 and the converging sidewalls generate vortices for maintaining the liquid flowing in the channels on one of the sidewalls until switched by operation of the pin.
The switching element is bistable such that it is in one stable state or the other which is maintained in that condition by the feedback constituted by the vortex 30 which is generated by a portion of the power stream which is peeled off by the opposite wall. Since the chamber is of the cross-over type, it serves to isolate the interaction region from pressures downstream of the throat or outlet.
Fig. 3 illustrates diagrammatically a conventional fuel system (referred to in the art as the "Bosch" fuel injection system) in which a tank T delivers fuel via pump 50 through a fuel filter 51 to a fuel rail 52 which has the pressure therein regulated by a compensated pressure regulator having a spring biased diaphram 54 defining the regulator chamber into two chambers, one side of which is coupled to the air intake manifold 60 by a compensating air pressure line 61. The fuel injectors 71, 72 have a solenoid control injection valve which is typically biased closed by a spring so that a large electrical current is required to open the valve. The fuel management system for the internal combustion engine of the automobile includes an onboard computer which is supplied with data signals from sensors monitoring various engine operating parameters, such as rpm, temperature, exhaust gas characteristics, mass air flow, etc., and determines the proper fuel-air ratio for fuel economy, efficiency and smoothness of engine operations and compliance with emission standards. As diagrammatically illustrated, the computer 75 supplies individual signals to control each of the solenoids 71S, 72S of the injectors 71 and 72, each of the injectors having a relatively large mass pintle 71P and 72P, respectively, which are seated in a valve seat (not shown) by a spring 71S, 72S for the purpose of injecting fuel into the intake manifold induction pipe 60-1, 60-2 for each cylinder of the engine. It will be appreciated that while the prior art system disclosed is for a conventional multi-point injection system, similar system is also used for single point injection where a single injector is typically included and mounted in the body of the throttle (referred in the art as throttle body injection or TBI).
The intake manifold 60 has a separate air induction pipe for each cylinder of the engine two of which are shown 60-1 and 60-2, each being provided with a separate fluidic injector which is connected in parallel to fuel supply or pipe rail 52. The same schematic applies to 4, 6 or 8 injectors. Air is drawn through air filter 81 and passes through the mass flow sensor 82 to throttle 83. Throttle plate 84 is controlled by the operator and controls the flow area in the throttle air passage and thus the mass air flow to the engine cylinders via the induction pipes for each cylinder.
A system incorporating the present invention is shown in Fig. 4 and includes the pump 50' for pumping fuel from the tank (not shown) through a filter 51' to a fuel rail 52' which supplies the fuel under pressure to each of the injectors 10-1, 10-2 which are fluidic fuel injectors having the silhouette illustrated diagrammatically in Fig. 1 with exemplary dimensions illustrated in Fig. 2. Fuel under pressure in fuel rail line 52' is introduced into the power nozzle 12 from rail 52' for each of the fuel injectors and in parallel. Fuel which is not delivered to the engine is returned at a somewhat lower pressure to a return fuel rail 95 from each of the bistable fluidic injectors whenever the fuel is traveling on the side 14 of chamber 13 taking the path indicated by the arrow 96 (Fig. 2c) and is returned to the tank via line 97. A fixed pressure regulator 53' has a diaphram 54' biased by a spring 55' so as to maintain the fuel pressure at a relatively constant value.
Air for aerating the fuel prior to injection into the induction pipe leading to the engine is supplied after being filtered and measured by mass flow sensor but prior to passing through the throttle on fuel injector air supply rail 98 which supplies air in parallel to each of the fuel injectors and the outlet leg or passage 17. The fixed pressure regulator 53' need not be compensated as in the case illustrated in Fig. 3.

Claims

1. A fuel injection system for an internal combustion engine, said system having computer means (22) for receiving a plurality of electrical signals (23) corresponding to engine operating parameters and producing electrical control signals for supplying fuel to said engine, a bistable fluidic switch (10) having a power nozzle (12) coupled to the supply of fuel under pressure, a chamber (13) having sidewalls (14, 15) leading to a common outlet (16) and a pair of output channels (17, 18) receiving fuel issuing through said power nozzle, one of said channels (17) leading to said internal combustion engine and the other of said channels (18) leading to said supply, and electromagnetic means (21) controlled by said control signals from said computer means (22) for controlling the state of said bistable switch (10) characterized by a flow control pin (19) controlled by said electromagnetic means (21) and positioned to be interposed in and removed from the fluid flow path in said power nozzle (12) in a region on one side of the center line through said power nozzle and upstream of the throat (12T) thereof, to switch the state of said bistable switch (10) and so change the one of said output channels (17, 18) in which fuel flows.

2. The fuel injection system defined in claim 1 including means (26) in the one of said output channels (17) leading to said engine for isolating said fluidic switch (10) from engine vacuum.

3. The fuel injection system defined in claim 1 including means (26) in one of said output channels (17) for supplying air to atomize the fuel flowing therein.

4. The fuel injection system defined in Claim 1 including means for assuring that in the absence of said pin (19) in the fuel flow path, said bistable fluidic switch (10) is in a predetermined one of its stable states to issue fuel into said other (18) of said channels.

5. The fuel injection system defined in claim 4 wherein the axis of said power nozzle (12) is at an angle relative to the axis of said chamber (13).

6. The fuel injection system defined in claim 1 in which there is a fuel injector for each cylinder of said engine, and a common fuel rail (52') to each said bistable fluidic switch (10-1; 10-2) and a common fuel return rail (95) connected to each said bistable fluidic switch.

7. A fuel injection system as defined in any of Claims 1 to 6 including means (98) for introducing air into the or each bistable fluidic switch (10-1; 10-2) to atomize said fuel before injection of same into an air intake manifold (60).

8. A fuel injection system as defined in any of Claims 1 to 7 including a solenoid (21) for controlling the position of the flow control pin (19).

9. A fuel injection system as defined in any of Claims 1 to 8 in which the flow control pin (19) moves along its own longitudinal axis.

10. A fuel injection system as defined in Claim 9 in which a spring (24) biases the flow control pin (19) to the setting in which it is removed from said fluid flow path.