GB2074233A - Fuel-handling arrangement in an I.C. engine fuel-injection system - Google Patents

Abstract

A jacket 48 for a fuel-injection valve 10 has a fuel inlet passage 28 communicating with a fuel accumulation chamber 32 and also has a fuel-exit passage 28 so that there is constant movement of fuel from the inlet passage through the accumulation chamber and out by way of the exit passage. The exit passage is inclined upwardly so that entrained vapour can escape into a collection chamber 34. <IMAGE>

Description

SPECIFICATION A hot fuel handling arrangement for a fuel injection system The invention pertains generally to electronic fuel injection systems and is more particularly directed to fuel delivery metering apparatus for such systems.

The majority of automobiles being built today have fuel systems which are either controlled by means of a carburetor or a fuel injection system.

The system being described herein is calculated to combine the advantages of both systems and either solve or ameliorate many of the inherent problems of the two systems.

In the case of a carburetor, while it has an advantage of low cost and low operating fuel pressure, there are many undesirable characteristics inherent to the use of a carburetor.

For example, the operation of a carburetor requires a continuous flow of fuel, the quantity of fuel being determined by the position of the throttle. It has been found that the fuel is not properly atomized and entrained in the air flow through the throat of the carburetor. Without proper atomization, the fuel distribution to the various cylinders is uneven, thereby causing a rich or lean mixture from one cylinder to another. This situation increases the objectionable emissions from the particular cylinder which is too rich or too lean relative to stoichiometric point. Also, relative to a fuel injection system, the carburetted system is inherently inaccurate in its fuel control whereby all of the cylinders may be operating at a point different from optimum.

Further, carburetted systems are typically operated in an open loop mode of operation. With this type of operation, the output of the engine exhaust system is not sensed to determine the quality of combustion which is occurring in the engine. Under these circumstances, the optimum air/fuei ratio is not achieved and higher emission levels are again experienced.

The shortcomings of a carburetted system have been somewhat eliminated by certain fuel injection systems on the market. With a fuel injection system, the fuel management is provided with a rather precise control of the fuel being fed to the engine which results in improved driveability without unwanted power surges, lower emission levels, convenient changes of the calibration of the system, and the system may be operated in a closed loop mode of operation.

As the importance of electronic fuel injection systems continues to increase because of their adaptability for economy, fuel metering and emission control, the actual valving devices or fuel injectors of such systems are becoming more critical to the operation of such systems as the limiting factors of operation.

The preferred valving device for the modern internal combustion engine injection system is the electro-magnetically operated solenoid type. The solenoid valve is relatively fast acting and accurate while being compatible and easily interfaced with modern electronic air/fuel ratio controllers.

Controliing the opening and closing times of the injectors electronically provides a powerful technique for adapting the air/fuel ratio with respect to a program or prestored schedule to control emissions. Normally, the electromagnetic injectors are either specifically designed for either single point or multipoint operation.

In the single point operation, usually one injector is configured to deiiver fuel at one general distribution point, conventionally the air induction bore of a throttle body connecting to a plane of a manifold arrangement. A fast acting high capacity solenoid valve is needed in this arrangement since the injector must work twice as fast as in a multipoint arrangement while delivering twice the fuel for an eight cylinder engine. An advantageous single point system specially adapted to a dual plane manifold arrangement is disclosed in our Patent Specification No. 1 ,58 1 ,708.

In a multipoint system, a plurality of points are injected in a localized manner, for example each individual cylinder of a multi-cylinder engine. A fuel rail or fuel manifold is required to supply these systems at relatively high pressures. This high pressure fuel enters one end of the injector and passes through a restrictive passage to where it is metered from an exit orifice into the vicinity of the intake valve of the cylinder. A multipoint fuel injection system of this type is illustrated in a U.S.

Patent No. 3,788,287.

With a multipoint system, there are problems involved in the hot starting of the automobile and hot fuel handling due to the fact that the injectors are positioned very close to the high heat areas of the engine, as are the fuel lines feeding the injectors. This creates vaporization of the fuel resulting in a low quantity of fuel being injected per pulse to create a lean air/fuel ratio. Further, the multipoint fuel injection system requires a high pressure fuel system with the inherent sealing problems and the cost of a high pressure pump.

An object of the present invention is to provide an improved arrangement for the handling of hot fuel in fuel injection systems of an internal combustion engine.

According to the invention there is provided a hot fuel handling arrangement for the fuel injection of an internal combustion engine at an injection point, said arrangement comprising: an independently formed injector jacket located at the injection point having an inlet fuel passage for receiving pressurized fuel and for communicating said fuel to an accumulation chamber defined by an inside wall of said injector jacket, said injector jacket further having a fuel exit passage directly connected to the accumulation chamber for communicating fuel from said accumulation chamber, said inlet fuel passage forming a circulation path with said exit passage to maintain a constant movement of fuel from said inlet passage through said accumulation chamber and out said exit passage, said circulation causing entrained vapor and bubbles within the system to move toward said exit passage, wherein said exit passage is elevated with respect to said inlet passage to enhance the flow of the entrained vapor and bubbles toward said exit passage.

The invention is particularly applicable for use with the fuel injection systems of our co-pending applications Nos. 7902175 and 8111162. The present application has been divided out from application No. 7902175 which describes and claims a single point fuel injection system.

Application No. 81111 62 is a further divisional application which describes and claims a fuel metering assembly which includes a rapid substitution injection valve for both single and multi-point fuel injection systems.

The invention will now be described by way of example with reference to the accompanying drawings, in which Figure 1 is a top view of a single point fuel injection system for a dual plane multi-cylinder induction manifold having a hot fuel handling arrangement according to the invention; Figure 2 is a reverse side view of the injection system illustrated in Figure 1; Figure 3 is an obverse side view of the fuel injection system illustrated in Figure 1; and Figure 4 is a cross-sectional side view of the injection system illustrated in Figure 1 and taken along lines 4-4 of that figure.

Figure 1 shows in a top view a fuel injection system in which rapid substitution injectors 8, 10 are mounted into an advantageous single point throttle body generally designated 12. Each injector 8, 10 is operable to meter fuel into an air induction bore 14 and 16 respectively. The air flow through the bores is controlled conventionally by a pair of ganged throttle plates 18 and 20 which rotate to open an increasing passageway to air flow in response to the operation of a throttle linkage 22.

Fuel enters the throttle body of the system from a fuel inlet passage 24 shown in a dotted configuration from a fuel inlet port 25 which is connected to a source of pressurized fuel (not shown). A cam operated fuel pump attached to a fuel line of a gas tank, as found in a conventional autombile, would be a preferred choice for the source. The source, as will be noted later, need only provide between 6-1 kg/cm2 of fuel pressure since the system is a low pressure fuel delivery apparatus. The usual high pressure fuel source for electronic fuel injection systems is not needed in this system with a resultant economy in overall fuel delivery cost.

From the inlet passage 24, the fuel passage 24 bifurcates into fuel delivery passages 26, 28 which open to accumulation chambers 30 and 32 as shown in phantom. The fuel continues its transmission from the accumulation chambers 30, 32 through the fuel delivery passages 26, 28 to a collection chamber 34 of a pressure regulator 37.

From the collection chamber 34, the fuel passes through a regulated pressure port 36 which communicates with a fuel exit passage 38 ending in a fuel exit port 40 where it is returned by conventional tubing or the like to the fuel reservoir or fuel tank.

The pressure regulator 37 controls the opening and closing of the regulated port 36 to provide a constantly recirculated fuel flow and substantially constant pressure at the accumulator chambers 30 and 32. The injectors 8, 10 then meterfuel from the accumulator chambers 30, 32 into the air induction bores 14 and 16 respectively in response to electrical control signals via control cables 42 and 44 which pass through a grommet 46. Ground cables 41,43 of the injectors 8, 10 are conveniently connected to the throttle body 1 2 at terminal post 45.

The electrical control signal is developed from an electronic control unit and provides signals for timing the opening and closing of the individual injection valves 8, 10. Although many electronic control units could be used for providing pulse width modulated control signals to the injection valves, the preferred timing and control unit for the illustrated single point system is described in Patent Specification No. 1,581,708 previously referred to.

As better illustrated in FIGURE 2, the fuel inlet port 25 is located below fuel exit port 40 and can be conveniently connected to conduit or fuel lines for recirculating the fuel by conventional fuel fittings 23, 35 respectively. Upstanding tabs 11, 13, 15 and 17 are provided along the periphery of the throttle body 12 for the mounting of an air cleaner as is generally known.

With reference now to Figures 2, 3, and 4, there is shown the mounting and support for one of the rapid substitution injectors, for example the injector referenced 10. The accumulation chamber 32 is defined as the inside bore or wall of a substantially cup-shaped injector jacket 48. Each injector jacket 48 is laterally supported in a coaxial relationship with its associated air induction bore by a bridge structure 53, including a lower wing 52 and an upper wing 54 shown in cross section.

The fuel delivery passage 28 is formed by an inner bore through the lower wing 52 and the upper wing 54. The bridge 53 as seen in FIGURE 3 is streamlined and suspends the injector jacket 48 above the throttle blade of the bore. The elongated shape of the injection valve 10 and injectorjacket 48 permit the air flow into the bore to flow freely around them and offer few projections to create turbulence.

The throttle blqde of each bore is controlled by the linkage 22 of FIGURE 3 to rotate open or closed in response to forces applied to pins 29, 31. For example, a spring can be connected to pin 31 to provide a closure torque on the throttle blade mounting rod 33 if the force is directed to the right as seen in the drawing. An operator controlled cable connected to pin 29 will provide an opening torque to rod 33 if the force it applies is also directed to the right.

With respect to FIGURE 4, the fuel delivery passage 28 is canted at an upward angle, for example in the preferred embodiment between 1 5--200 because this angle of bore provides a passage for vapor and air bubbles to pass to the collection chamber 34 instead of remaining in the accumulation chamber or passage. Importantly, according to one of the aspects of the invention, it has been found that even when an auto is parked on a hill this angle will provide enough upward bias to the vapor to allow it to collect and be dissipated in the chamber 34 instead of becoming a vapor lock in the passages or accumulation chamber.

The injector jacket 48 has upper and lower mounting apertures 56 and 58 respectively into which the injector 10 is adapted to mount directly.

The injector jacket 48 is further provided with a supporting shoulder 60 which is of slightly greater diameter than the body of the injector 10 and supports a mounting ring 62 press fitted onto the injector 10. An O-ring 64 hydraulically seals the abutment of the ring 62 and the shoulder 60.

This produces a very tight hydraulic seal without the necessity of providing a great deal of downward pressure on the injector to form a leak resistant type fitting. A simple spring-type clip 65 held by a screw 66 retains the injector in the jacket 48.

The lower mounting aperture 58 similarly receives a slightly smaller radial flange 57 of an injector end cap 59. The end cap further is provided with a larger radial flange 63 which is brought into abutment when the injector is inserted in the jacket 48. A suitably designed 0ring 68 is located in the recess in the end cap 59 defined by the radial flange 57 and radial flange 63 and thus seals the abutment of the mounting shoulder 61 and the flange 63.

It is evident that the injector 10 may be mounted or removed from the jacket 48 with relative ease. The injector is devoid of any hard fuel connection from the pressurized source and is provided functionally as an electronically controlled valve to meter fuel from the accumulation chamber 32. If an injector becomes non-functional in the system, it may be replaced without disconnecting and reconnecting fuel supply lines. Further, the fuel delivery passages remain integral or intact when the injector is replaced and do not have to be retuned.

The sealed accumulation chamber 32 configuration has the advantage of providing a substantially constant fuel pressure to the injector 10 and will not, even under many rapid openings, produce a substantial pressure drop. The accumulation chamber 32 also aids in handling hot fuel in concert with the elevated fuel delivery passage 28. The chamber 32 provides a volume in which vapor and bubbles can be transported or rise to the passage 28 and away from the injector metering tip. The inlet orifices to the injection valve are located below the delivery passage 28 to provide this action. Importantly, this will not permit the vapor to be trapped within the injection valve where it will be harder to purge. The fuel volume contained within the valve is also relatively small for this reason.

Figure 4 further illustrates that the injector 10 for this single point configuration is a wide-angled spray injector. The wide-angled (in cross section) or hollow cone spray pattern is more advantageous than a straight pattern injection when the injector 10 is mounted concentrically with the air induction bore 1 6 and above the throttle blade as shown by the drawings.

Generally, the air for the system is inducted through larger and larger areas or openings as the throttle plate rotates. These openings are defined by the air induction bore wall and the throttle blade periphery. If the fuel is injected in a hollow conical spray that is aimed or directed toward these openings, the turbulence created by the air being accelerated through the restriction between the throttle blade and the air induction wall will cause good vaporization and fuel distribution.

The angle of the spray cannot be too great or it will wet the walls of the air induction bore, and cannot be too small or it will be injected upon the throttle plate and condense. Therefore, a compromise has to be worked out taking into account the distance the injector is from the throttle and the bore opening diameter. Generally for the embodiment shown in the figure, an included spray angle of between 600 to 800 is thought to provide an optimum result as to vaporization and mixing with the inducted air.

Throttle bodies with different sized bores will have the mounting distances adjusted accordingly.

The throttle body is further provided with a vacuum sensing port 74 that communicates to the air induction bore 1 6 in proximity to the closed throttle position of the throttle. As the air is restricted between the throttle plate 20 and the inner wall of the bore, a vacuum or pressure drop will occur. This vacuum is integrated in a sealed measuring chamber 76 and communicated to a sensor via a tubularfitting 78. As-seen in Figure 1, the level of vacuum delivered from the tubular fitting 78 may be averaged with the vacuum of the other air induction bore 14 as via a similar tubular fitting 80 and common conduit 81 to provide a totalized vacuum signal from the entire throttle body via a pressure sensor 83.

Claims (5)

1. A hot fuel handling arrangement for the fuel injection of an internal combustion engine at an injection point, said arrangement comprising: an independently formed injector jacket located at the injection point having an inlet fuel passage for receiving pressurized fuel and for communicating said fuel to an accumulation chamber defined by an inside wall of said injector jacket, said injector jacket further having a fuel exit passage directly connected to the accumulation chamber for communicating fuel from said accumulation chamber, said inlet fuel passage forming a circulation path with said exit passage to maintain a constant movement of fuel from said inlet passage through said accumulation chamber and out said exit passage, said circulation causing entrained vapor and bubbles within the system to move toward said exit passage, wherein said exit passage is elevated with respect to said inlet passage to enhance the flow of the entrained vapor and bubbles toward said exit passage.

2. A hot fuel handling arrangement as claimed in Claim 1 , said arrangement further comprising electronically controlled fuel injection valve means to meter said fuel from the accumulation chamber into said injection point, wherein said fuel injection valve includes fuel inlets which are located below both said inlet and exit fuel passages to further enhance the flow of entrained vapor and bubbles toward said exit passages.

3. A hot fuel handling arrangement as claimed in Claim 1 or 2, wherein said circulation of fuel is maintained at a constant pressure by connecting said inlet fuel passage to a pressurized source and by connecting said exit fuel passage to a pressure regulator.

4. A hot fuel handling arrangement as claimed in any one of the preceding claims, wherein said elevation of said exit fuel passage over said inlet fuel passage is provided by two in line bores canted at an angle of at least 1 50 relative to horizontal.

5. A hot fuel handling arrangement for the fuel injection of an internal combustion engine at an injection point, said arrangement being substantially as described and as shown in the accompanying drawings.