Title:
FUEL-INJECTION APPARATUS FOR INTERNAL-COMBUSTION ENGINES
United States Patent 3592177
Abstract:
Fuel-injection apparatus for use with internal-combustion engines having an intermediate reservoir which stores and makes available the quantity of fuel to be injected for each fuel-injection operation. The intermediate reservoir is provided with two chambers separated from each other by a movable dividing wall. The first of these chambers is connected between a pressurized fuel supply and/or the second of these chambers. The second chamber is selectively connected between the first chamber and at least one fuel-injection nozzle. A spring is arranged in the second chamber to bias the movable wall in the direction of enlargement of the second chamber. The first chamber may be selectively connected by one three-way valve or by two one-way valves. Means are provided to adjust the quantity of fuel injected in response to the requirements of the engine. The devices may be used individually, or grouped together for multicylinder engines.
US Patent References:
Fuel injection apparatus
French - May 1952 - 2598528
HIGH-SPEED FUEL INJECTION SYSTEM
Bassot et al. - July 1969 - 3456628
SYSTEM FOR PRESSURIZING AND RELIEVING LIQUIDS IN CONDUITS
Bassot et al. - January 1970 - 3490425
FUEL INJECTION SYSTEM FOR INTERNAL COMBUSTION ENGINES
Bassot et al. - June 1970 - 3516395
Fuel injection apparatus
French - May 1952 - 2598528
HIGH-SPEED FUEL INJECTION SYSTEM
Bassot et al. - July 1969 - 3456628
SYSTEM FOR PRESSURIZING AND RELIEVING LIQUIDS IN CONDUITS
Bassot et al. - January 1970 - 3490425
FUEL INJECTION SYSTEM FOR INTERNAL COMBUSTION ENGINES
Bassot et al. - June 1970 - 3516395
Application Number:
04/863945
Publication Date:
07/13/1971
Filing Date:
10/06/1969
View Patent Images:
Export Citation:
Assignee:
Teldix GmbH (Heidelberg, DT)
Primary Class:
Other Classes:
123/446, 123/478
International Classes:
F02D9/00; F02M59/14; F02M59/00; F02M51/00
Field of Search:
123/32E,139,139E,139A,139.14,119,139AW
Primary Examiner:
Goodridge, Laurence M.
Claims:
I claim
1. Fuel-injection apparatus for internal-combustion engines comprising, in combination:
2. a housing, and
3. dividing means arranged within said housing and dividing the same into first and second chambers, said dividing means being movable to and fro to increase the volume of one of said chambers while decreasing the volume of the other of said chambers,
4. spring means arranged within said housing and biasing said dividing means in the direction of enlargement of said second chamber;
5. Fuel-injection device as defined in claim 1 wherein said connection means includes a three-way valve.
6. Fuel-injection device as defined in claim 2, further comprising:
7. Fuel injection device as defined in claim 1 wherein said connection means includes two two-way valves, one of said two-way vaLves, being connected between said first chamber and said second chamber.
8. Fuel injection device as defined in claim 4 wherein the other of said two two-way valves is connected between said first chamber and said constant-pressure, pressurized fuel supply.
9. Fuel injection device as defined in claim 4 wherein the other of said two two-way valves is connected between said second chamber and said injection means.
10. Fuel injection device as defined in claim 4 wherein said valves are electromagnetic valves.
11. Fuel injection device as defined in claim 4, further comprising:
12. Fuel injection device as defined in claim 4, further comprising:
13. Fuel injection device as defined in claim 1 wherein said reservoir means includes a plurality of housing, with a plurality of said second chambers connected with one another so that they can be emptied through said injection means.
14. Fuel injection device as defined in claim 10 wherein said injection means includes a common injection line connected to a plurality of electromagnetically controlled injection valve.
15. Fuel injection device as defined in claim 10 wherein said housing have different capacities.
16. Fuel injection device as defined in claim 10 comprising selecting means by which dependent upon the desired quantity of fuel those housing are selected for evacuation whose capacities together approach the desired quantity of fuel.
1. Fuel-injection apparatus for internal-combustion engines comprising, in combination:
2. a housing, and
3. dividing means arranged within said housing and dividing the same into first and second chambers, said dividing means being movable to and fro to increase the volume of one of said chambers while decreasing the volume of the other of said chambers,
4. spring means arranged within said housing and biasing said dividing means in the direction of enlargement of said second chamber;
5. Fuel-injection device as defined in claim 1 wherein said connection means includes a three-way valve.
6. Fuel-injection device as defined in claim 2, further comprising:
7. Fuel injection device as defined in claim 1 wherein said connection means includes two two-way valves, one of said two-way vaLves, being connected between said first chamber and said second chamber.
8. Fuel injection device as defined in claim 4 wherein the other of said two two-way valves is connected between said first chamber and said constant-pressure, pressurized fuel supply.
9. Fuel injection device as defined in claim 4 wherein the other of said two two-way valves is connected between said second chamber and said injection means.
10. Fuel injection device as defined in claim 4 wherein said valves are electromagnetic valves.
11. Fuel injection device as defined in claim 4, further comprising:
12. Fuel injection device as defined in claim 4, further comprising:
13. Fuel injection device as defined in claim 1 wherein said reservoir means includes a plurality of housing, with a plurality of said second chambers connected with one another so that they can be emptied through said injection means.
14. Fuel injection device as defined in claim 10 wherein said injection means includes a common injection line connected to a plurality of electromagnetically controlled injection valve.
15. Fuel injection device as defined in claim 10 wherein said housing have different capacities.
16. Fuel injection device as defined in claim 10 comprising selecting means by which dependent upon the desired quantity of fuel those housing are selected for evacuation whose capacities together approach the desired quantity of fuel.
Description:
CROSS REFERENCE TO RELATED APPLICATION AND BACKGROUND OF THE INVENTION
The present invention relates to a fuel-injection apparatus for internal-combustion engines of the type having an intermediate reservoir which stores and makes available the quantity of fuel to be injected. This reservoir is divided into an antechamber and a pump chamber by a movable wall. Such a fuel-injection device was proposed in U.S. Pat. application Ser. No. 814,310, filed Apr. 9th, 1969, and assigned to the assignee of this application. Due to a pressure increase in the antechamber, the movable wall is moved so that the fuel previously measured out in the pump chamber is pressed out through an injection nozzle.
This earlier proposal has the advantage when compared with known fuel-injection apparatus which use electronic means to time the operation of the injection valve, that the measuring process can be performed more precisely because it is separated from the injection process. In addition, the solution mentioned above also has the advantage that the injection pressure is always the same during the injection process, and can be set at an arbitrarily high level.
SUMMARY OF THE INVENTION
It is the object of the present invention to retain these advantages, i.e. constant injection pressure and separate measuring, while providing a more simplified fuel-injection device. It is proposed according to the present invention to bias the movable wall with a spring which tends to enlarge the pump chamber. Further, it is provided that the antechamber can be selectively connected with either a fuel feeding line, which is always under pressure, and/or the pump chamber. Several variations of this concept are set out, each with different operation and different advantages. These possible solutions will first be discussed in principle.
The selective connection is most simply accomplished by means of a three-way valve. When this valve is in one position, the pump chamber is emptied and the antechamber is simultaneously filled from the fuel feeding line. When this valve is in the other position, the contents of the antechamber are transferred to the pump chamber. The amount of fuel injected is determined by the position of the movable wall at the beginning of the injection cycle. A means is provided for determining the position of the movable wall; which means causes a switching signal to be emitted to the three-way valve when the movable wall has performed a pumping stroke appropriate for the operating conditions of the motor. The advantage of this solution is, in particular, the only one three-way valve is required, although an accurate volume measurement is achieved.
In the other embodiments of the present invention, two one-way magnetic valves are employed. One of these valve is disposed in the line between the antechamber and the pump chamber as a so-called bypass valve; whereas the other valve is disposed either in the fuel feeding line, or between the pump chamber and the injection nozzle. In this case, the amount to be injected is held in readiness during the relatively long time period between the injection processes. The injection is accomplished by opening the valve disposed either in the fuel feeding line or the injection nozzle. The required amount is measured out by opening the bypass valve. Here, the movable wall, due to the force exerted by the spring, pushes as much liquid from the antechamber into the pump chamber as is required for the next injection process. It is possible to either determine the filling stroke by means of a positioning device which closes the bypass valve when the movable wall is in the desired position, or to control the duration of the flow through the bypass valve by means of a timing device. By inserting a choke into the bypass line, the measuring process can be slowed down to such an extent that the entire line interval between the injection cycles is used up. This choking makes it possible to ignore the response times of the valves, which are subject to certain fluctuations during their lifetime, within a given temperature range, while retaining high accuracy.
Finally, it is proposed to combine a number of single, different capacity systems in such a manner that a discontinuous quantity measurement is obtained. This is accomplished by connecting the different capacity pump chambers together so they eject through a common injection nozzle. For this application the first-mentioned version with a three-way valve is preferably, since it requires the least number of valves.
In the arrangement for multiple-cylinder internal-combustion engines mentioned above, the quantity of fuel delivered by each cylinder is either a set value (preferably the full capacity of the cylinder) or zero. Thus, the device for determining the position of the movable wall is eliminated. Instead of one injection nozzle per arrangement, there is then provided a common injection line from where the individual engine cylinders can be selectively served through a plurality of electromagnetically controlled injection valves.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram of a first embodiment of the instant invention.
FIG. 2 shows the pulse diagram for the embodiment of FIG. 1.
FIG. 3 is a schematic diagram of a second embodiment of the instant invention.
FIG. 4 shows the pulse diagram for the embodiment of FIG. 3.
FIG. 5 is a schematic diagram of a third embodiment of the instant invention.
FIG. 6 shows the pulse diagram for the embodiment of FIG. 5.
FIG. 7 is a schematic diagram of a plurality of devices according to the embodiment of FIG. 1 arranged in series.
FIG. 8 shows the pulse diagram for the arrangement of FIG. 7.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows a schematic representation of a fuel pump 1 and a three-way valve 2. A double arrow 3 represents the movable element of the three-way valve. A housing 50 is constructed in the form of a cylinder in which a close fitting piston 4 can move back and forth. This piston represents a movable wall, and divides the cylinder into an antechamber 5 and a pump chamber 6. In the pump chamber 6 a compression spring 7 is arranged which tends to hold piston 4 in its upper end position. In the illustrated switching position of the three-way valve 2, the chamber 5 is connected with the pump chamber 6 through valve 2 and bypass line 8. When the movable element 3 is positioned on the left side of valve 2, the chamber 5 is connected with the fuel feeding line 9 of the pump. At the bottom of the pump chamber 6 an injection nozzle 10 is connected which normally is held shut by a sealing element 11, seated by a spring 12. This nozzle seal is so dimensioned that it opens immediately when the pressure of the conveying pump 1 is present in the pump chamber 6. The configuration of the sealing element 11 also enhances the atomization of the fuel.
To electrically measure the position of piston 4 in its cylinder, there is provided a pickup 13 which is indicated only schematically. This pickup may contain, e.g., inductances, which are varied by the movement of the piston 4 of ferromagnetic material. The signal from the pickup 13 is fed to a comparison circuit 15 through a line 14. It compares this signal with a signal from the output 16 of a nominal value generator 17. The operating values of the internal-combustion engine are fed to the nominal valve generator 17 in a suitable manner. Two such operating values or parameters, i.e. the temperature T and the speed n, are illustrated as examples. The pickup signal is normally less then the nominal value. When piston 4 has covered a certain distance on its way down, however, the pickup signal increases to above the nominal value. In this case the comparison circuit 15 emits a pulse I 2 which continues until the pickup signal falls below the nominal value again as the piston returns to its upper position.
In addition to I 2 , a pulse I 1 also acts on a bistable multivibrator, or flip-flop 18, whose output pulse I 3 controls the three-way valve 2. I 1 is a short pulse which is taken in a known manner from the crankshaft of the internal-combustion engine. It determines the moment at which the fuel injection begins. When taken with the pulse sequence shown in FIG. 2, the arrangement according to FIG. 1 operates in the manner set out below.
Starting from the position illustrated in FIG. 1, the system is actuated by the crankshaft pulse I 1 (FIG. 2). The flip-flop is transferred to its other stable state by pulse I 1 , and pulse I 3 appears at its output. The three-way valve 2 is switched in turn by pulse I 3 , so that the movable element 3 is now in its left-hand position (not shown). This is the beginning of the fuel-injection process. The pressure produced by pump 1 pushes piston 4 downward, and opens the sealing element 11 of the injection nozzle 10. With the downward movement of the piston, there appears an increasing pickup signal in line 14. As soon as it has exceeded the nominal value coming through line 16 from the nominal value generator 17, pulse I 2 appears at the output of the comparison circuit 15. The leading edge of this pulse transfers the flip-flop back into its original, stable position and thus terminates pulse I 3 . The three-way valve 2 switches back to its right-hand position once pulse I 3 ceases so that the chamber 5 is now connected with the pump chamber 6 again, and the piston 4 can be moved back upward into its end position by the force of spring 7. Shortly after this return movement begins, the pickup signal has fallen below the nominal value again; which means the end of pulse I 2 . The device now remains at rest until the next crankshaft pulse I 1 initiates a repetition of the same procedure.
In the embodiment according to FIG. 3 an electromagnetically controlled one-way valve, the so-called bypass valve 20, takes the place of the three-way valve 2. Moreover, an electromagnetically controlled injection valve 21 is provide which normally closes the fuel-injection nozzle 22. A pickup 19 is similar to pickup 13, except the leads are reversed from those of FIG. 1 so that it furnishes the weakest pickup signal in the lower end position of piston 4 and the strongest pickup signal in the upper end position. Consequently, the output signal I 5 of the comparison circuit 15 will appear when the piston moves upward. I 5 flips the flip-flop 18, whose output signal I 6 controls the bypass valve 20, back to its nonconducting, stable position. A crankshaft pulse I 4 controls the injection valve 21 and is also fed to the flip-flop 18 through an inverter 24. A choke 23 can also be inserted in the bypass 8. The function of this choke is set out below.
The pulse diagram of FIG. 4 shows the sequence of operation of the embodiment of FIG. 3. In the situation illustrated in FIG. 3, piston 4 rests in its center position in cylinder 50 because the pressure on each side of the piston is equal. Both valves (20, 21) are closed. When the crankshaft pulse I 4 appears, the injection valve 21 opens and the pressure produced by pump 1 performs the injection stroke by moving piston 4 down until it reaches its lower end position. Pulse I 4 continues at least as long as it takes for a full injection stroke to be completed and then terminate. Injection valve 21 then closes. Since the pulse I 4 is fed to the flip-flop 18 through an inverter 24, the trailing edge of the pulse triggers the flip-flop instead of the leading edge. When the flip-flop has been transferred to its conducting, stable state, pulse I 6 is produced to open bypass valve 20. The piston now moves upward under the force of spring 7, a process which, with suitable choke action, can taken up the entire time until the start of the next injection cycle. The point at which the piston is at rest again is determined by the nominal value generator 17. This is the point where the pickup signal exceeds the nominal value, and pulse I 5 appears at the output of the comparison circuit. I 5 throws the flip-flop 18 back into the nonconducting position, thus terminating pulse I 6 and closing the bypass valve 20. This results, however, in the interruption of the piston movement. Depending on whether the piston comes to rest more at the top of cylinder 50 or more at the bottom, the next injection will be larger or smaller. Thus, the amount of fuel injected is a function of the parameters fed value generator 17.
This arrangement according to FIG. 5 differs from that of FIG. 3 by the insertion of an electromagnetically controlled injection valve 25 into the feeder line 9. The injection opening 10 is held shut by a sealing element 11 under spring pressure in the manner of the embodiment of FIG. 1. Valve 25 is controlled by a crankshaft pulse I 7 , and the bypass valve 20 by a pulse I 8 which originates in a timer 26. This timer is triggered by crankshaft pulse I 7 , whereas its duration is set by nominal value generator 17.
The arrangement of FIG. 5 operates as follows: At the outset the piston is in the illustrated center position because the force exerted on the piston by the pressure of the liquid in the sealed chamber 5 is compensated by the tension in spring 7. The injection process is now initiated by crankshaft pulse I 7 (see FIG. 6) which opens valve 25. The piston moves down and forces the quantity of fuel in pump chamber 6 through opening 10. Pulse I 7 is is simultaneously also fed to timer 26. Its trailing edge triggers this timer and, thus, determines the moment of initiation of pulse I 8 . The pulse length is synonymous with the so-called "dosaging time" which is determined by the setting of the timer 26 in cooperation with the nominal value generator 17. The bypass valve 20 is open during this time, and the piston 4 is permitted to perform its upward return movement. The longer the dosaging time is, the further upward the piston moves and the larger will e be the amount of fuel injected in the next injection stroke.
The quantity of fuel to be injected, therefore, is determined in this case only by the dosaging time. It must be realized, however, that this dosaging time may be relatively long (the length can be selected by appropriate choking) so that a high accuracy of dosaging is assured, independent of the operational parameters.
This method of valve control can also be used with the arrangement according to FIG. 3, while the control based on measuring the position of piston 4 (FIGS. 1 and 3) can also be employed for the arrangement of FIG 5.
The final embodiment of the present invention is shown in FIG. 7. We find three different cylinders systems, each similar to that of FIG. 1, with three different cylinders 27, 28 and 29, each of these three cylinders has different piston displacement and their pistons principally only perform full strokes form one end position to the other. These three cylinders have three associated three-way valves 30 to 32. The center connection of these three-way vales is always connected to the antechamber; the left connection leads, via a bypass 8' --8"' to the pump chamber; and the right connection leads to a common fuel feeding line 40. The pump chambers are connected with one another by an injection line 39; which leads to four electromagnetically controlled injection valves 33 to 36. The three-way valves 30--32 are triggered by pulses I 9a to I 9c , which pulses originate from a pulse generator 37. The injection valve 33--36 are opened by pulses I 10a to I 10d . These latter pulses are fed by means of a distributing device 38, from the engine crankshaft (or from a camshaft driven by a crankshaft) at those moments when, in this four-cylinder internal-combustion engine, the fuel must be injected into one of the individual cylinders. The electronic pulse generator 37 has individual engine operating parameters and the angular position of the crankshaft fed into it, and feeds outpulses of equal length to a selected number of the three-way valve control lines I 9a --I 9c . According to this embodiment, the dosaging does not occur by filling a cylinder to a different level, but by calling on one or more cylinders to deliver fuel to fuel feeding line 40. This will be explained below in further detail with the aid of the pulse diagram of FIG. 8.
Starting with all three pistons in the upper position and the movable elements of the three-way valve closing feeder line 40 as shown in FIG. 7, it shall be assumed that the internal-combustion engine demands that the full capacity of the pump chambers by injected. In this case, the pulse generator 37 which has already been fed the parameters and crankshaft pulse emits three pulses I 9a to I 9c simultaneously. These pulses (I 9a to I 9c ) move the moving element of valves 30--32 to the left. This only prepares the injection mechanism and nothing changes for the moment. During the duration of pulses I 9 , the first crankshaft pulse I 10a arrives at the injection valve 33 of the first cylinder. This injection valve opens, and the pressure produced by pump 1 drives all three pistons downward so that the contents of all three cylinders are injected. Pulse I 10a continues just long enough for the pistons to safely reach their lower end position. At the same time, or shortly thereafter, pulses I 9 also end, and the three-way valves 30--32 return to their rest or right-hand position. This makes it possible for the pistons to return to their upper end position. The next pulse series I 9 again begins either shortly before or simultaneously with pulse I 10b which opens the injection valve 34 of the second cylinder. This process is appropriately continued until changes in the operating parameters adjust the pulse generator 37 in such a manner that it emits a different selection of the three possible pulses I 9a to I 9c , e.g., only I 9a and I 9c . This is shown in the last two columns of the diagram, where pulse I 9b is shown only in dashed lines. The absence of pulse 9b causes the piston of cylinder 28 to remain at rest and the injected quantity comprises only the contents of cylinders 27 and 29.
It will be realized of course that any number of cylinders can be used with the embodiment of FIG. 7. The more cylinders that are provided, the more finely graduate will be the dosaging.
It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations.
The present invention relates to a fuel-injection apparatus for internal-combustion engines of the type having an intermediate reservoir which stores and makes available the quantity of fuel to be injected. This reservoir is divided into an antechamber and a pump chamber by a movable wall. Such a fuel-injection device was proposed in U.S. Pat. application Ser. No. 814,310, filed Apr. 9th, 1969, and assigned to the assignee of this application. Due to a pressure increase in the antechamber, the movable wall is moved so that the fuel previously measured out in the pump chamber is pressed out through an injection nozzle.
This earlier proposal has the advantage when compared with known fuel-injection apparatus which use electronic means to time the operation of the injection valve, that the measuring process can be performed more precisely because it is separated from the injection process. In addition, the solution mentioned above also has the advantage that the injection pressure is always the same during the injection process, and can be set at an arbitrarily high level.
SUMMARY OF THE INVENTION
It is the object of the present invention to retain these advantages, i.e. constant injection pressure and separate measuring, while providing a more simplified fuel-injection device. It is proposed according to the present invention to bias the movable wall with a spring which tends to enlarge the pump chamber. Further, it is provided that the antechamber can be selectively connected with either a fuel feeding line, which is always under pressure, and/or the pump chamber. Several variations of this concept are set out, each with different operation and different advantages. These possible solutions will first be discussed in principle.
The selective connection is most simply accomplished by means of a three-way valve. When this valve is in one position, the pump chamber is emptied and the antechamber is simultaneously filled from the fuel feeding line. When this valve is in the other position, the contents of the antechamber are transferred to the pump chamber. The amount of fuel injected is determined by the position of the movable wall at the beginning of the injection cycle. A means is provided for determining the position of the movable wall; which means causes a switching signal to be emitted to the three-way valve when the movable wall has performed a pumping stroke appropriate for the operating conditions of the motor. The advantage of this solution is, in particular, the only one three-way valve is required, although an accurate volume measurement is achieved.
In the other embodiments of the present invention, two one-way magnetic valves are employed. One of these valve is disposed in the line between the antechamber and the pump chamber as a so-called bypass valve; whereas the other valve is disposed either in the fuel feeding line, or between the pump chamber and the injection nozzle. In this case, the amount to be injected is held in readiness during the relatively long time period between the injection processes. The injection is accomplished by opening the valve disposed either in the fuel feeding line or the injection nozzle. The required amount is measured out by opening the bypass valve. Here, the movable wall, due to the force exerted by the spring, pushes as much liquid from the antechamber into the pump chamber as is required for the next injection process. It is possible to either determine the filling stroke by means of a positioning device which closes the bypass valve when the movable wall is in the desired position, or to control the duration of the flow through the bypass valve by means of a timing device. By inserting a choke into the bypass line, the measuring process can be slowed down to such an extent that the entire line interval between the injection cycles is used up. This choking makes it possible to ignore the response times of the valves, which are subject to certain fluctuations during their lifetime, within a given temperature range, while retaining high accuracy.
Finally, it is proposed to combine a number of single, different capacity systems in such a manner that a discontinuous quantity measurement is obtained. This is accomplished by connecting the different capacity pump chambers together so they eject through a common injection nozzle. For this application the first-mentioned version with a three-way valve is preferably, since it requires the least number of valves.
In the arrangement for multiple-cylinder internal-combustion engines mentioned above, the quantity of fuel delivered by each cylinder is either a set value (preferably the full capacity of the cylinder) or zero. Thus, the device for determining the position of the movable wall is eliminated. Instead of one injection nozzle per arrangement, there is then provided a common injection line from where the individual engine cylinders can be selectively served through a plurality of electromagnetically controlled injection valves.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram of a first embodiment of the instant invention.
FIG. 2 shows the pulse diagram for the embodiment of FIG. 1.
FIG. 3 is a schematic diagram of a second embodiment of the instant invention.
FIG. 4 shows the pulse diagram for the embodiment of FIG. 3.
FIG. 5 is a schematic diagram of a third embodiment of the instant invention.
FIG. 6 shows the pulse diagram for the embodiment of FIG. 5.
FIG. 7 is a schematic diagram of a plurality of devices according to the embodiment of FIG. 1 arranged in series.
FIG. 8 shows the pulse diagram for the arrangement of FIG. 7.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows a schematic representation of a fuel pump 1 and a three-way valve 2. A double arrow 3 represents the movable element of the three-way valve. A housing 50 is constructed in the form of a cylinder in which a close fitting piston 4 can move back and forth. This piston represents a movable wall, and divides the cylinder into an antechamber 5 and a pump chamber 6. In the pump chamber 6 a compression spring 7 is arranged which tends to hold piston 4 in its upper end position. In the illustrated switching position of the three-way valve 2, the chamber 5 is connected with the pump chamber 6 through valve 2 and bypass line 8. When the movable element 3 is positioned on the left side of valve 2, the chamber 5 is connected with the fuel feeding line 9 of the pump. At the bottom of the pump chamber 6 an injection nozzle 10 is connected which normally is held shut by a sealing element 11, seated by a spring 12. This nozzle seal is so dimensioned that it opens immediately when the pressure of the conveying pump 1 is present in the pump chamber 6. The configuration of the sealing element 11 also enhances the atomization of the fuel.
To electrically measure the position of piston 4 in its cylinder, there is provided a pickup 13 which is indicated only schematically. This pickup may contain, e.g., inductances, which are varied by the movement of the piston 4 of ferromagnetic material. The signal from the pickup 13 is fed to a comparison circuit 15 through a line 14. It compares this signal with a signal from the output 16 of a nominal value generator 17. The operating values of the internal-combustion engine are fed to the nominal valve generator 17 in a suitable manner. Two such operating values or parameters, i.e. the temperature T and the speed n, are illustrated as examples. The pickup signal is normally less then the nominal value. When piston 4 has covered a certain distance on its way down, however, the pickup signal increases to above the nominal value. In this case the comparison circuit 15 emits a pulse I 2 which continues until the pickup signal falls below the nominal value again as the piston returns to its upper position.
In addition to I 2 , a pulse I 1 also acts on a bistable multivibrator, or flip-flop 18, whose output pulse I 3 controls the three-way valve 2. I 1 is a short pulse which is taken in a known manner from the crankshaft of the internal-combustion engine. It determines the moment at which the fuel injection begins. When taken with the pulse sequence shown in FIG. 2, the arrangement according to FIG. 1 operates in the manner set out below.
Starting from the position illustrated in FIG. 1, the system is actuated by the crankshaft pulse I 1 (FIG. 2). The flip-flop is transferred to its other stable state by pulse I 1 , and pulse I 3 appears at its output. The three-way valve 2 is switched in turn by pulse I 3 , so that the movable element 3 is now in its left-hand position (not shown). This is the beginning of the fuel-injection process. The pressure produced by pump 1 pushes piston 4 downward, and opens the sealing element 11 of the injection nozzle 10. With the downward movement of the piston, there appears an increasing pickup signal in line 14. As soon as it has exceeded the nominal value coming through line 16 from the nominal value generator 17, pulse I 2 appears at the output of the comparison circuit 15. The leading edge of this pulse transfers the flip-flop back into its original, stable position and thus terminates pulse I 3 . The three-way valve 2 switches back to its right-hand position once pulse I 3 ceases so that the chamber 5 is now connected with the pump chamber 6 again, and the piston 4 can be moved back upward into its end position by the force of spring 7. Shortly after this return movement begins, the pickup signal has fallen below the nominal value again; which means the end of pulse I 2 . The device now remains at rest until the next crankshaft pulse I 1 initiates a repetition of the same procedure.
In the embodiment according to FIG. 3 an electromagnetically controlled one-way valve, the so-called bypass valve 20, takes the place of the three-way valve 2. Moreover, an electromagnetically controlled injection valve 21 is provide which normally closes the fuel-injection nozzle 22. A pickup 19 is similar to pickup 13, except the leads are reversed from those of FIG. 1 so that it furnishes the weakest pickup signal in the lower end position of piston 4 and the strongest pickup signal in the upper end position. Consequently, the output signal I 5 of the comparison circuit 15 will appear when the piston moves upward. I 5 flips the flip-flop 18, whose output signal I 6 controls the bypass valve 20, back to its nonconducting, stable position. A crankshaft pulse I 4 controls the injection valve 21 and is also fed to the flip-flop 18 through an inverter 24. A choke 23 can also be inserted in the bypass 8. The function of this choke is set out below.
The pulse diagram of FIG. 4 shows the sequence of operation of the embodiment of FIG. 3. In the situation illustrated in FIG. 3, piston 4 rests in its center position in cylinder 50 because the pressure on each side of the piston is equal. Both valves (20, 21) are closed. When the crankshaft pulse I 4 appears, the injection valve 21 opens and the pressure produced by pump 1 performs the injection stroke by moving piston 4 down until it reaches its lower end position. Pulse I 4 continues at least as long as it takes for a full injection stroke to be completed and then terminate. Injection valve 21 then closes. Since the pulse I 4 is fed to the flip-flop 18 through an inverter 24, the trailing edge of the pulse triggers the flip-flop instead of the leading edge. When the flip-flop has been transferred to its conducting, stable state, pulse I 6 is produced to open bypass valve 20. The piston now moves upward under the force of spring 7, a process which, with suitable choke action, can taken up the entire time until the start of the next injection cycle. The point at which the piston is at rest again is determined by the nominal value generator 17. This is the point where the pickup signal exceeds the nominal value, and pulse I 5 appears at the output of the comparison circuit. I 5 throws the flip-flop 18 back into the nonconducting position, thus terminating pulse I 6 and closing the bypass valve 20. This results, however, in the interruption of the piston movement. Depending on whether the piston comes to rest more at the top of cylinder 50 or more at the bottom, the next injection will be larger or smaller. Thus, the amount of fuel injected is a function of the parameters fed value generator 17.
This arrangement according to FIG. 5 differs from that of FIG. 3 by the insertion of an electromagnetically controlled injection valve 25 into the feeder line 9. The injection opening 10 is held shut by a sealing element 11 under spring pressure in the manner of the embodiment of FIG. 1. Valve 25 is controlled by a crankshaft pulse I 7 , and the bypass valve 20 by a pulse I 8 which originates in a timer 26. This timer is triggered by crankshaft pulse I 7 , whereas its duration is set by nominal value generator 17.
The arrangement of FIG. 5 operates as follows: At the outset the piston is in the illustrated center position because the force exerted on the piston by the pressure of the liquid in the sealed chamber 5 is compensated by the tension in spring 7. The injection process is now initiated by crankshaft pulse I 7 (see FIG. 6) which opens valve 25. The piston moves down and forces the quantity of fuel in pump chamber 6 through opening 10. Pulse I 7 is is simultaneously also fed to timer 26. Its trailing edge triggers this timer and, thus, determines the moment of initiation of pulse I 8 . The pulse length is synonymous with the so-called "dosaging time" which is determined by the setting of the timer 26 in cooperation with the nominal value generator 17. The bypass valve 20 is open during this time, and the piston 4 is permitted to perform its upward return movement. The longer the dosaging time is, the further upward the piston moves and the larger will e be the amount of fuel injected in the next injection stroke.
The quantity of fuel to be injected, therefore, is determined in this case only by the dosaging time. It must be realized, however, that this dosaging time may be relatively long (the length can be selected by appropriate choking) so that a high accuracy of dosaging is assured, independent of the operational parameters.
This method of valve control can also be used with the arrangement according to FIG. 3, while the control based on measuring the position of piston 4 (FIGS. 1 and 3) can also be employed for the arrangement of FIG 5.
The final embodiment of the present invention is shown in FIG. 7. We find three different cylinders systems, each similar to that of FIG. 1, with three different cylinders 27, 28 and 29, each of these three cylinders has different piston displacement and their pistons principally only perform full strokes form one end position to the other. These three cylinders have three associated three-way valves 30 to 32. The center connection of these three-way vales is always connected to the antechamber; the left connection leads, via a bypass 8' --8"' to the pump chamber; and the right connection leads to a common fuel feeding line 40. The pump chambers are connected with one another by an injection line 39; which leads to four electromagnetically controlled injection valves 33 to 36. The three-way valves 30--32 are triggered by pulses I 9a to I 9c , which pulses originate from a pulse generator 37. The injection valve 33--36 are opened by pulses I 10a to I 10d . These latter pulses are fed by means of a distributing device 38, from the engine crankshaft (or from a camshaft driven by a crankshaft) at those moments when, in this four-cylinder internal-combustion engine, the fuel must be injected into one of the individual cylinders. The electronic pulse generator 37 has individual engine operating parameters and the angular position of the crankshaft fed into it, and feeds outpulses of equal length to a selected number of the three-way valve control lines I 9a --I 9c . According to this embodiment, the dosaging does not occur by filling a cylinder to a different level, but by calling on one or more cylinders to deliver fuel to fuel feeding line 40. This will be explained below in further detail with the aid of the pulse diagram of FIG. 8.
Starting with all three pistons in the upper position and the movable elements of the three-way valve closing feeder line 40 as shown in FIG. 7, it shall be assumed that the internal-combustion engine demands that the full capacity of the pump chambers by injected. In this case, the pulse generator 37 which has already been fed the parameters and crankshaft pulse emits three pulses I 9a to I 9c simultaneously. These pulses (I 9a to I 9c ) move the moving element of valves 30--32 to the left. This only prepares the injection mechanism and nothing changes for the moment. During the duration of pulses I 9 , the first crankshaft pulse I 10a arrives at the injection valve 33 of the first cylinder. This injection valve opens, and the pressure produced by pump 1 drives all three pistons downward so that the contents of all three cylinders are injected. Pulse I 10a continues just long enough for the pistons to safely reach their lower end position. At the same time, or shortly thereafter, pulses I 9 also end, and the three-way valves 30--32 return to their rest or right-hand position. This makes it possible for the pistons to return to their upper end position. The next pulse series I 9 again begins either shortly before or simultaneously with pulse I 10b which opens the injection valve 34 of the second cylinder. This process is appropriately continued until changes in the operating parameters adjust the pulse generator 37 in such a manner that it emits a different selection of the three possible pulses I 9a to I 9c , e.g., only I 9a and I 9c . This is shown in the last two columns of the diagram, where pulse I 9b is shown only in dashed lines. The absence of pulse 9b causes the piston of cylinder 28 to remain at rest and the injected quantity comprises only the contents of cylinders 27 and 29.
It will be realized of course that any number of cylinders can be used with the embodiment of FIG. 7. The more cylinders that are provided, the more finely graduate will be the dosaging.
It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations.