Fuel Injection System

The invention relates to a fuel injection system of the type described herein and finally claimed. A fuel injection system is already known in which a spring reservoir is provided in the fuel supply line for the purpose of preventing vapor bubbles after the internal combustion engine is turned off and to compensate for volumetric changes when the engine temperature is dropping after the engine is turned off or volumetric changes caused by leakage of fuel out of the system. However, in such a system there is the disadvantage that the reservoir volume cannot be made to be as large as desired, so that when the fuel injection system is not in operation the movable reservoir element contacts its end stop after a relatively short time, and further vapor bubble information can no longer be prevented and a further compensation for a lessening in fuel volume is no longer possible. This often causes misfiring, in the event of restarting of the internal combustion engine, until such time as the system is again completely filled with fuel.

The fuel injection system in accordance with the invention has the advantage over the prior art that the fuel injection system is filled with fuel before the starter motor of the internal combustion engine is actuated, so that a more secure start is assured for the internal combustion engine.

As a result of the features described in the dependent claims, further advantageous embodiments and improvements of the fuel injection system given in the main claim are possible.

The invention will be better understood as well as further objects and advantages thereof become more apparent from the ensuing detailed description of preferred embodiments taken in conjunction with the drawings.

FIG. 1 shows a first exemplary embodiment of a fuel injection system; and

FIG. 2 is a second exemplary embodiment of a fuel injection system.

Turning now to FIG. 1, there will be seen a first embodiment of a fuel injection system including an intake manifold 1 having a conical section 2 which contains an air flow rate member 3 beyond which there is located an induction tube region 4 containing an arbitrarily settable throttle valve 5. Intake air flows through the induction tube in the direction of the arrow to one or more cylinders 8 of an internal combustion engine.

In the present case, the air flow rate member 3 is a baffle plate disposed transversely with respect to the direction of air flow and capable of displacement within the conical region 2 of the induction tube in accordance with a certain function of the air flow rate through the tube. The air pressure between the air flow rate member 3 and the throttle valve 5 will be constant provided that the restoring force acting on the air flow rate member 3 is constant and that the air pressure ahead of the member 3 is also constant. The air flow rate member 3 controls the opening of a metering and distribution valve assembly 10. The air flow rate member 3 includes a main operating lever 11 and an auxiliary or correction lever 12. The motion of the air flow rate member 3 is transmitted by the operating lever 11 which is pivoted on the same shaft 13 as the correction lever 12 and which actuates the control slide 14 which is the movable member of the metering and distribution valve assembly 10. A mixture control screw 15 permits an adjustment of the desired fuel-air mixture.

Fuel is supplied by an electric fuel pump 19 which aspirates the fuel from a fuel tank 20 and delivers it through a storage container 21, a filter 22 and a fuel line 23 to the fuel metering and distribution assembly 10. A fuel system pressure controller 24 maintains the system pressure in the fuel injection system constant.

The fuel supply line 23 splits into several branches which lead to first chambers 26 of the fuel valve assembly 10, whereby one side of a diaphragm 27 in each chamber is affected by fuel pressure. The first chambers 26 also communicate with an annular groove 28 of the control slide 14. Depending on the axial position of the control slide 14, the annular groove overlaps control slits 29 to varying degrees permitting fuel to flow into second chambers 30 which are divided from the first chambers 26 by the diaphragm 27. From the second chambers 30, fuel flows through fuel injection lines 33 to the individual injection valves 34 which are located in the vicinity of the engine cylinders 8 in the induction tube region 7. The diaphragm 27 is the movable valve member of a control valve which is held open by a spring 35 when the fuel injection system is not operating. The diaphragm boxes defined, in each case, by a chamber 26 and a chamber 30, insure that the pressure drop at the metering valve 28, 29 is substantially constant independently of the relative overlap between the annular groove 28 and the control slits 29, i.e., independently of the fuel quantity flowing to the injection valves 34.

During a pivoting displacement of the operating lever 11, the air flow rate member 3 is moved into the conical region 2 so that the varying annular cross section between the flow rate member and the conical wall has a certain function with respect to the displacement of the air flow rate member 3.

The restoring force exerted on the control slide 14 and thus on the air flow rate member 3 may be generated by means of a compression spring 45, which is supported on the air flow rate member housing and urges the air flow rate member 3 in the closing direction. However, it is also sufficient to have an agreement between the lever weight and a compensation weight 44 on the other side of the pivot point 13. A control pressure line 36 branches off from the fuel supply line 23 downstream of the first chamber 26 of the control valves 26, 30, 33, which line 36 is separated from the fuel supply line 23 by an uncoupling throttle 37. A pressure chamber 39 communicates via a damping throttle 38 with the control pressure line 36 and the control slide 14 which includes a front face 16 projecting into this pressure chamber 39.

Downstream of the damping throttle 38 a further throttle restriction 46 is provided in the control pressure line 36, through which the fuel can flow out of the control pressure line 36, without pressure, into a return flow line 43 and from there back to the fuel tank 20. The pressure of the fuel in the pressure chamber 39, first, generates a restoring force on the air flow rate member 3 and, second, serves to damp the adjustment movement of the air flow rate member 3.

When the internal combustion engine is being turned off, the control slide 14 of the fuel metering and distribution valve 10 is displaced by the compression spring 45, via the air flow rate member 3, into a position in which the control slits 29 are closed by the control slide 14 but the front face 16 of the control slide 14 opens a flushing line 47, which branches off from the fuel supply line 23 and discharges into the pressure chamber 39. At the same time, the front face 16 of the control slide 14, in this position, opens flushing channels 48, which connect the pressure chamber 39 with each second chamber 30 of the control valves. Upstream of the further throttle restriction 46, a reservoir chamber 49 of a hydraulic reservoir 50 having a movable reservoir or diaphragm member 51, which acts counter to a compression spring 52, is connected with the control pressure line 36. The movable reservoir member 51, as shown by the broken line 53, is coupled with an electric pressure switch 54, which in the illustrated position closes an electrical circuit 55, which is in contact with the vehicle battery 56. The ignition switch 58 of the internal combustion engine is disposed in the connecting line 57 between the vehicle battery 56 and the pressure switch 54.

Now, looking to the left of FIG. 1, an electromagnet 65 is disposed in the electrical circuit 55 which in the illustrated position of the previously mentioned pressure switch 54, in which the electrical circuit 55 is in contact with the vehicle battery 56, is energized and thus moves the movable valve parts 66 of the flushing valve 59 in the opening direction. The flushing valve 59 controls discharge lines 60, which branch off from each injection valve 34 and when the flushing valve 59 is opened, discharge via the return flow lines 43', 43 into the fuel tank 20. The discharge lines 60 are disposed at the injection valves 34 in such a manner that the fuel supplied via the injection lines 33 to each injection valve 34 flows through the injection valve and subsequently proceeds into the particular discharge line 60.

The mode of operation of the fuel injection system described herein is as follows.

Within a relatively short time after the internal combustion engine is turned off, the fuel pressure in the fuel injection system has dropped to such an extent that the reservoir member or diaphragm 51 of the reservoir 50 assumes a position in which the pressure switch 54 assumes the illustrated position, at which time it then connects the electrical circuit 55 of the electromagnet 65 with the connecting line 57. If the ignition switch 58 of the engine is now closed, then the electromagnet 65 is energized and thus the flushing valve 59 and the discharge lines 60 from the injection valves 34 to the return flow line 43', 43 are opened. Simultaneously with the closing of the ignition switch 58, the electrical circuit of the electric fuel pump 19 is closed, so that the fuel pump 19 supplies fuel out of the fuel tank 20 via the fuel supply line 23 into the first chambers 26 and subsequently via the uncoupling throttle 37 into the control pressure line 36 and on the other side via the flushing line 47 into the pressure chamber 39 and from there into the second chambers 30 of the control valves 26, 30, 33. From the second chambers 30 of the control valves, the fuel, controlled by the diaphragm 27, proceeds into the injection lines 33 and the injection valves 34 and from there into the discharge lines 60 to the flushing valve 59, via which the fuel proceeds into the return flow line 43', 43. A pressure control 69 can be disposed in the return flow line 43' which maintains a flushing pressure which is greater than the fuel vapor pressure, so as to prevent the formation of new fuel vapor bubbles in the hot system as well. Simultaneously, the reservoir 50 begins to fill and the reservoir member 51 moves against the force of the compression spring 52 toward the right as seen in the drawing and upon reaching a predetermined filling status actuates the pressure switch 54 in such a manner that the electrical circuit 55 of the electromagnet 65 is opened and the flushing valve 59 closes. Simultaneously with the interruption of the connection with the electrical circuit 55, the pressure switch 54 closes an electrical circuit 61 of the starter motor 62 of the internal combustion engine, which now, with a closed starter switch 63, begins to run and starts the internal combustion engine. The air for combustion now induced by the internal combustion engine moves the air flow rate member 3 against the force of the compression spring 45 in the opening direction, as a result of which the control slide 14 is lifted to such an extent that the front face 16 of the control slide 14 closes both the discharge opening of the flushing line 47 and the discharge opening of the flushing channels 48 into the pressure chamber 39 and a fuel quantity corresponding to the induced air quantity can be metered out between the annular groove 28 and the control slits 29.

The embodiment of the fuel injection system in accordance with the invention thus assures that all the lines and units of the fuel injection system are flushed with fuel before the engine is started and thus are filled, so that difficulties in starting the engine as a result of insufficient fuel supply are effectively prevented. The flushing time before the engine is started is determined by means of the reservoir 50 depending on the degree of evacuation or of vaporization in the lines. The reservoir 50 thus represents a timing device and is designed in such a manner that a pressure prevails in the injection lines 33 during the flushing process which is below the opening pressure of the injection valves 34.

Turning now to the second exemplary embodiment of the fuel injection system shown in FIG. 2, the elements thereof which are identical to those of the first embodiment of FIG. 1 are given the same reference numerals. In this view, the movable reservoir member 51 of the reservoir 50 disposed in the control pressure line 36 is directly coupled to the movable valve elements 66 of the flushing valve 59 and can move these elements against the force of a flushing spring 67 in the closing direction. As in the first exemplary embodiment of FIG. 1, the reservoir 50 serves in the second embodiment of FIG. 2 as a timing device, which below a certain fuel pressure in the control pressure line 36 holds the flushing valve 59 open, so that the fuel injection system is flushed with fuel after the actuation of the ignition switch 58 until such time as the predetermined fuel pressure in the control pressure line 36 is exceeded and the reservoir member 51 closes the flushing valve 59. Simultaneously with exceeding the predetermined fuel pressure in the pressure control line 36, the pressure switch 54 is displaced by a pressure-sensing member 68, a pressure capsule, for instance, via an actuation member 53 shown in broken lines into a position in which it closes the electrical circuit 61 of the starter motor 62, which now, with a closed starting switch 63, begins to run. The subsequent function corresponds to that described in connection with FIG. 1.

Compared with the first exemplary embodiment of this invention, the second exemplary embodiment thereof is simplified by means of the direct coupling of the reservoir 50 to the flushing valve 59 and enables easy exertion of the closing force onto the flushing valve 59 by means of an appropriately large embodiment of the reservoir member 51.

The foregoing relates to preferred embodiments of the invention, it being understood that other embodiments and variants thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.