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(11) | EP 0 200 063 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Fuel injection system |
| (57) A bistable fluidic switch (10) is switched from its stable state by a pin (19) inserted
in the power nozzle (12) of the bistable fluidic switch (10), the pin (19) being controlled
by an electromagnetic actuator (21) which is controlled from an electronic computer
(22). The fluidic switch element (10) has a cross-over type interaction region (13)
and a common outlet (16) leading to a pair of output passageways (17, 18), one of
which (18) returns fuel to the supply tank, and the other of which (17) leads to the
air intake manifold of the engine. Air is introduced into the output passageway (17)
leading to the engine so as to air atomize the fuel before injection of same into
the air intake manifold. |
REFERENCE TO RELATED APPLICATIONS
[0001] This application is related to the application of Ronald D. Stouffer, U.S. Serial No. 470,791, filed February 28, 1983 and entitled "Improved Fluidic Transducer for Switchinq Fluid Flow", assigned to the assignee hereof.
BACKGROUND AND BRIEF DESCRIPTION OF THE INVENTION
[0002] 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,
[0003] smoothness of enqine 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 hiqhly accurate control siqnals 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 loadinq 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 phemplet "High Technology from Buick", "the 3.8 SF Turbo".
[0004] 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 hiqh pressure rail). Current systems (such as those marketed by Robert Bosch) use approximately 27 to 37 psi to avoid the formation of vapor bubbles. Lower pressure systems require less complexity and less expensive pump.
[0005] 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.
[0006] According to one major feature of the invention, a switch pin is projected into and out of intrusion position in the flow path of fluid in the power nozzle of the fluidic element to cause switching in the chamber of the bistable switch. In other words. 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, eliminatinq small flow passaqes 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 the power nozzle is canted relative to the axis of the chamber of the fluidic element so that in the absence of the pin, the switch is in one predetermined state and is switched form that state to the other state by pin intrusion and always returns to that predetermined state on removal of the intrusion pin.
[0007] 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 füel/air spray which is of primary importance in fuel/air mixture preparation. Improved spray (smalller 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 idle and light load conditions, when the vacuum is high - (15-20 in.hg.) 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 enqine 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 enouqh air added to greatly effect engine vacuum. The power nozzle then becomes the major source of pressure drop of the fluid in the system.
[0008] In the preferred embodiment, both major features are utilized but it will be appreciated that either feature can be used independently of the other and still obtain advantages of the invention.
[0009] Thus, the basic objective of the invention is to provide an improved fuel injection system for internal combustion engines. A further object of the invention is to provide an improved bistable fluidic switch which has no control ports or passages; and a further object of the invention is to provide an improved fuel preparation by the addition of filtered and nonitored air to fuel for internal combustion engines prior to induction in the engine.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] 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:
Fiq. 1 is a isometric view of a bistable fluidic switch according to the invention.
Fig. 2a is an enlarqed plan silhouette view of an actual operating unit with exemplary dimensions thereon.
Fiq. 2b is a silhouette of Fig. 2 showing the flow path with the pin intruding or projecting position in a flow path in the power nozzle.
Fig. 2c shows the flow paths with the pin in unintrudinq or retracted position,
Fiq. 3 is a schematic block diaqram 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
[0011] 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 converqe relative to common outlet 16 leading to a first output passaqe 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.
[0012] Switch control pin or pintle 19 is moved through the transverse bore hole 20 by electromaqnetic coil 21 which receives control siqnals from conventional on-board computer 22 which. in turn, receives a plurality of enqine and performance data parameter signals on its input lines 23 from the various engine sensors and siqnal transducers (not shown). A spring 24 biases the pintle or pin and its drivinq 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 chanqes 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 is 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 air flow is computed based on manifold absolute pressure, the injector is accounted for by its effect on manifold pressure. In a fuel meterinq system which makes use of direct air mass flow measurement. the source of inject air is downstream of thehe 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 hiqh <15 - 20 inhj). Coincidentally, the enqine combustion is most sensitive to droplet size at idle and liqht load conditions.
[0013] 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.
[0014] 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.
[0015] As shown in Fiq. 2b, when the pin 19 is in an intruding position, it is specifically located in a reqion to the right of the center line therouggh the power nozzle 12 and upstream of the theroad 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 deqrees relative to the axis of chamber 13 so that the fuel will flow-through passage 18 and return to the tank (as shown in Fiq. 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 he let 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 Fiq. 2b.
[0016] 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 is 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.
[0017] 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.
[0018] Referring now to Figs. 3 and 4. Fiq. 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 oressure therein regulated by a compensated pressure regulator havinq 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 70, 71 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 monitorinq various engine operating parameters, such as rpm, temperature, exhaust gas characteristics, mass air flow, etc.. an 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 injector 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 infection 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).
[0019] 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.
[0020] The system incorporating the present invention is shown in Fig. 4 and includes the pump 50 for pumping fuel from the tank tnot shown) through a filter 51 to a fuel rail 52 which supplies the fuel under pressure to each of the injectors 90, 91 which are fluidic fuel injectors having the silhouette illustrated diagrammatically in Fig. 1 with exemplary dimensions illustrated in Fiq. 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. 2) 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.
[0021] 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 passaqe 17. The fixed pressure regulator 53' need not be compensated as in the case illustrated in Fiq. 3.
a flow control pin controlled by said electromagnetic means and positioned to be interposed in and removed by a fluid flow path in said power nozzle to switch the state of said bistable switch and change the one of said output channels in which fuel flows.
a short fuel passage coupling said fuel to the air intake manifold of said engine.
a supply of air. and
means for introducina said air in said short small fuel passageway to air atomize said fuel before injection of same into said air intake manifold.
a power nozzle coupled to said supply of fuel.
a chamber for receiving fuel from said power nozzle,
a pair of output passages, each of which is adapted to receive fuel when said bistable fluidic outlet is in one or the other of its states. respectively, and
means for switching the states of said bistable fluidic switch.a solenoid for controlling the position of said pin, and neans connectinq said solenoid to said computer.