Method And Apparatus For Injecting Fuel Into The Cylinders Of A Multicylinder Piston-type Internal Combustion Engine

Abstract

Fuel injection apparatus for multicylinder engines comprising a fuel pump, delivery lines to the individual cylinders, separate means to measure the volume of fuel flowing through those lines, and means to adjust the injection pressure in those lines or the injection opening times therefrom into the individual cylinders.

Description

The present invention pertains to a method for the introduction of fuel into the working cylinders of a multicylinder piston-type internal combustion engine. In accordance with the invention the quantities of fuel injected into the individual cylinders in given time intervals are measured during operation of the engine and corrections are introduced into the injection in dependence of the measurements made, these corrections serving to equalize the quantity of fuel supplied to the individual cylinders.

In the apparatus of the invention for practice of the method thereof in an engine having plural cylinders and an injection system including at least one fuel pump with fuel lines leading to the individual cylinders, measuring devices are provided in the fuel lines leading to the individual cylinders, these devices serving to measure the volume of fuel passing through those lines. Moreover, corrective devices are provided, allocated to the individual cylinders, and which serve to adjust the fuel supply to those cylinders.

In multicylinder piston-type internal combustion engines difficulty is experienced in equalizing the quantities of fuel supplied to the separate cylinders. Thus, large differences can appear in the quantities of fuel delivered to the individual cylinders by the volumetric fuel pumps now commonly employed, these difficulties being especially troublesome at high injection pressures. This produces unequal thermal loading of the cylinders with danger of mechanical overloading of individual cylinders. The result is to impose a lower limit of safe loading than would otherwise be necessary.

It has already been proposed to employ time-controlled valves for control of the injection into the individual cylinders. These valves open the fuel delivery lines for precisely measured intervals of time having a duration of a few milliseconds and thereupon close again. The fuel is drawn from storage reservoirs which are fed from a feed pump. This mode of operation has the particular advantage that electrically operated valves can be used, and this produces a simplification in the mechanical construction of the apparatus. It is, however, subject to the shortcoming that the quantities of fuel which achieve injection during the specified time intervals may undergo substantial variation one from one cylinder to another because for example of the various nozzle cross sections of the individual injectors.

It is an object of the invention to provide a method and apparatus by means of which these disadvantages are minimized and which makes possible a uniform distribution of fuel to the individual cylinders. Simultaneously, the invention makes possible the use of the time-controlled injection valves and consequently, a substantial simplification of the engine consistently with a uniform supply of fuel to all cylinders at all load levels imposed on the engine.

In accordance with the invention it is possible to vary the injection pressure or the injection time duration to the individual cylinders in accordance with correction values. Which of these possibilities is preferable in an individual case depends to a large extent on the construction of the injection system.

Advantageously the correction values are applied in a time-delayed manner. In this way the supplementary control provided by the correction signals is made to be a stable one.

As to the apparatus, the measurement devices may take the form of volumetric motors having rotors built into the fuel delivery lines, the motion of these rotors being monitored by scanning devices. Preferably the rotors take the shape of gear pumps and scanning devices are devices which operate without electrical contacts. Thus, they may operate magnetically, inductively, or capacitively. With this construction it is possible for the complete measurement device for any fuel line to be in a closed housing having no mechanically movable parts on the exterior thereof to be sealed off. At the high pressures involved a sealing of, for example, a shaft passing to the exterior of the housing would be a difficult problem.

The correction devices may take the form of means for adjustment of the injection pressure at the individual cylinders. Thus, adjustable throttling devices may be employed as correction elements, these throttling devices being disposed, for example, in the fuel delivery lines. They may however be disposed on the suction side of plural fuel pumps allocated to the cylinders. Such throttling devices make possible a simple adjustment of the streaming resistance of the individual hydraulic lines and injection valves.

It is also possible to employ correction devices which serve mutually to change the swept volumes of volumetric fuel pumps of the individual cylinders.

Owing however to the uniformization of the fuel feed achieved, the invention has important advantages also in the case of mechanically or hydraulically actuated time-controlled injection valves.

In the several fuel lines, time-controlled valves may be arranged, which may be electromagnetically operated for example. In this way, as previously mentioned, a simple construction of the engine can be achieved, in which the cam shafts heretofore required with their cam drives can be eliminated.

For time-controlled injection valves, the correcting devices may take the form of control means effecting a mutual variation of the open times of the several valves, the open time of a valve otherwise open too long being shortened while that of a valve otherwise open too short a time is lengthened. It is thus possible to obtain a design that, besides exceptional simplicity, has the further advantage that it can be actuated in simple manner by an electronic controller.

It is also possible to provide a controller that makes a comparison of the values taken by measurement at individual cylinders and actuates the correcting means through control signals according to the comparative data obtained. This controller may determine the deviations of the readings of the several cylinders from the reading of a cylinder serving as master cylinder. Or it may form a mean of the readings at the various cylinders, determine the deviations of the several cylinders from that means, and set up the control signals accordingly.

In this way it is possible to provide the engine with a continuously and precisely operating control wherein, depending on the nature of the deviations to be expected, either the one or another type of control may have special advantages.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be further explained in terms of a number of presently preferred nonlimitative exemplary embodiments and with reference to the accompany drawings in which:

FIG. 1 is a diagram of a diesel engine having three cylinders and incorporating fuel control apparatus according to the invention, with manual setting of throttling means;

FIG. 2 is a transverse sectional view of one form of fuel measuring apparatus according to the invention;

FIG. 3 is a diagrammatic representation of another form of apparatus according to the invention in conjunction with a diesel engine;

FIGS. 4 to 7, are diagrams useful in explaining the apparatus of FIGS. 1 and 3;

FIG. 8 is a further diagrammatic showing similar to that of FIGS. 1 and 3 but illustrating the apparatus of the invention in conjunction with an engine having volumetric injection pumps of modern type;

FIG. 9 is a block diagram of an electronic controller for the apparatus of FIG. 3; and

FIGS. 10 and 11 show two different forms for the correction signal generator 110 of FIG. 9.

Like reference characters denote similar elements of structure throughout the general FIGS.

DESCRIPTION OF PREFERRED EMBODIMENTS

In FIG. 1, a diesel engine 1 having three cylinders a, b, c is provided with a fuel pump 2. By way of a pressure regulator 3, pump 2 feeds fuel lines 4, 5 and 6 leading to cylinders a, b, c. In fuel lines 4 to 6, measuring means 7 are arranged, connected to indicating instruments 8. Electromagnetically actuated injection valves 9 are arranged in the fuel lines 4 to 6, just upstream of the several cylinders, and preferably at the outlets of the lines. Manually adjustable throttling means 10 are also provided in lines 4 to 6. When the injection system includes separate fuel reservoirs associated with the individual cylinders, the throttling means 10 for each cylinder are arranged between its reservoir and the injection valve 9. The electromagnetic injection valves 9 are controlled from an injection controller 11 by way of electric signal lines 12, 13, 14. Controller 11 receives a set value signal from a line 15, representative for example of a desired engine speed, and an actual value signal via signal line 16 from the output side of the engine. The signal on line 16 may represent for example engine speed, or some other operating variable. In the embodiment shown, the engine 1 drives an electric generator 17. In addition, the controller 11 may be connected by a signal line 18 (shown dotted) to the pressure regulator 3.

During operation of the engine, the pump 2 feeds fuel at high pressure, e.g., up to 1,000 kg./cm..sup.2 or more, into the fuel lines 4 to 6. The pressure regulator 3 either holds the pressure in the fuel lines 4 to 6 constant or, if it is equipped to handle the signal on line 18, it may adjust that pressure according to operating conditions. The regulator 3 may for example act on the pump 2 by way of a signal line 19. By way of signal lines 12 to 14, the controller 11 delivers control signals to the valves 9, so that they are opened at specified times and for specified time durations. Upon opening of an injection valve, the fuel in injected into the combustion chamber of the cylinder in question at the fuel line pressure. In this process it is possible either to keep the pressure in the fuel lines constant by operation of the pressure regulator 3 and to adjust the open time of the injection valves to the instantaneous load on the engine, or else the injection time may be held constant and the injected fuel volume may be varied by control of pressure in the fuel lines 4 to 6 with the aid of the regulator 3.

In the embodiment shown in FIG. 1, the readings of the several measuring means 7 may be read off at intervals on the indicating instruments 8. If major deviations in the flow of fuel fed to the individual cylinders thus appear, the throttling means 10 can be adjusted manually to equalize the deliveries. If for example the flow of fuel carried by one of the lines 4 to 6 is greater than that of the others, its throttling means 10 will be adjusted in closing direction, and vice versa.

FIG. 2 shows a preferred embodiment for the measuring device 7. Tow gears 21 in mesh with each other are disposed in a housing 21, inserted into a fuel line such as the line 4. The two gears form a volumetric hydraulic motor. Except for the line 4, housing 20 is closed on all sides, and no shafts pass from the gears to the outside of the housing. For development of a signal representative of the fuel flowing through the line, scanning means 22 are provided inside housing 20. The housing 20 may for example be made of nonmagnetic material and the gears 21 of ferromagnetic material. In that case, the scanning means 22 may include an electromagnetic coil with a core, the passing of the individual teeth of the nearer gear setting up electrical impulses in the coil. Alternatively the gears 21 and housing 20 may be made of an insulating material, the ends of the teeth being provided with electrically conductive material. The scanning means 22 may then include a coil to which alternating current is supplied. When a tooth passes, the electrical impedance of the coil is varied, and this can be utilized to set up an impulse.

The embodiment of FIG. 3 differs from that of FIG. 1 in that the measuring means 7 of FIG. 3 are provided with output signal lines 30, 31, 32 leading to a controller 33, replacing the controller 11 of FIG. 1. The controller 33 modulates the control signals which it delivers to lines 12 to 14 according to the data in signal lines 30 to 32. In the event of excessive supply of fuel to one cylinder, its injection time is shortened accordingly, and vice versa.

FIGS. 4 to 7 illustrate control of fuel supply and correction thereof in accordance with the invention by operation on the pressure in the fuel line and by operation on the open time of the injection valves. The injection times in the several cylinders a, b, c are plotted along the horizontal time-axis t. The vertical axis p represents the pressures in their respective fuel lines.

In FIG. 4, the basic quantity injected per operating cycle of the engine cylinder and at a given load on the engine corresponds to the rectangle M of altitude h and time duration M/h. Owing to unlike streaming conditions in the lines 4 to 6 to the various cylinders however, equal areas do not necessarily imply equal fuel quantities. Upon an increase in load, the controller 11 of FIG. 1 or 33 of FIG. 3 lengthens the open time of the injection valves, so that additional quantities of fuel are received, indicated by the rectangles N, likewise of altitude h and of time duration N/h. Correction for unequal deliveries to the various cylinders is made, in the case of FIG. 1, by resetting the throttling means 10 in one or more of the fuel lines with resulting changes of injection pressure upstream of the injection valve which are indicated by the areas 0 (added) and P (subtracted). That is, to increase the fuel injected, as indicated by the added area 0 in FIG. 4a, the throttling device 10 of the cylinder a is loosened to facilitate the flow of fuel through line 4. To reduce the flow of fuel, as indicated by the subtracted area P, the throttling device 10 on line 6 is lightened, to further restrict the flow of fuel through line 6.

The diagram of FIG. 4 corresponds for example to the embodiment of FIG. 1. It is immaterial in this connection whether the throttling means 10 are set by hand or automatically by a suitable control. The representation in FIG. 4 does not attempt to reflect the influence on the level of fuel pressure exerted by controller 11 on pressure regulator 3 by way of signal line 18. The cylinder b, whose injection flow is not corrected, acts as a master cylinder. This means that its fuel flow is taken as a datum, and the fuel deliveries to the other cylinders are adjusted to match it, with of course some time delay. The meaning of FIG. 4 thus is that by manual or automatic means, the throttles 10 on lines 4 and 6 are adjusted to raise the pressure at the injector in line 4 by the height of the area 0 and to reduce it at the injector in line 6 by the height of the area P so as to obtain in cylinder a quantity of injected fuel represented by the pressure-time product making up areas M, N and O together, equal to the quantity of fuel injected into cylinder b and which is represented in FIG. 4b by the sum of the areas M and N. In cylinder c there is obtained an equal quantity of injected fuel, but since the time rate of injection is a different function of pressure, this equal quantity is represented in FIG. 4c as the sum of the time-pressure products M and N less the time-pressure product P, M and N having the same areas in FIG. 4c as in FIG. 4a and 4b.

The diagram in FIG. 5 illustrates the operation of an embodiment of the invention in which the basic control of injection rate as well as the correction thereof as between cylinders are effected by pressure variation. The open time of the injection valves is in this case constant. Thus, the quantity of fuel injected into all cylinders is, to a first order of approximation, that given by the time-pressure product area M. Upon an increase in load, a quantity of fuel is added represented by the supplementary area Q, this addition being made by an increase of pressure, for example by operation of the pressure regulator 3 in FIG. 1. In addition, for correction of deficient injection to cylinders a and c, corrective pressure increases represented by the heights of the areas O and P in FIG. 5 are made by adjustment of the throttling devices 10 on lines 4 and 6, the correction 0 being in the positive direction (more fuel) and the correction P being in the negative direction, i.e., a subtraction from area Q in FIG. 5c. FIG. 5 thus illustrates operation of a fuel injection control system of the type shown in FIG. 1, with pressure regulated as a function of load by the pressure regulator 3 and with constant injection time.

In the diagram of FIG. 6, the injection pressure is kept constant, and the adjustment for load as well as the correction as between cylinders is made by varying the injection time. To a basic injection flow M there is added upon increase of load the quantity N, by a uniform extension of the injection time at all cylinders. Additional corrections of injection time are made, represented by areas R (positive) at cylinder a and S (negative) at cylinder c.

The diagram of FIG. 6 corresponds to the embodiment of FIG. 3 with a regulator 33 as illustrated in FIGS. 9 and 10.

Finally, FIG. 7 shows a diagram corresponding to injection control for response to load change by control of injection pressure, and correction as between cylinders by variation of injector open time.

The embodiment of FIG. 3 may operate in this manner, if the controller 33 thereof operates on pressure regulator 3 by way of signal line 18 and thereby controls the time rate at which fuel is injected while the injectors are open. The signals in lines 12, 13 and 14, which control the open times of the injection valves, then carry the correction signals as well.

FIG. 8 illustrates application of the invention to diesel engines having the usual now current volumetric injection pumps. The engine 1 is provided with injection pumps 80, each of which is assigned to one of the fuel lines 4 to 6. The pumps 80 are driven by the cam shaft of the engine, and are controlled from a control rod 81 by a lever 82 of a controller 83.

The pumps 80 of FIG. 8 are volumetric pumps, intended to deliver a constant volume of fuel at ever stroke, which volume is supposed to be the same for the pumps of all three cylinders. Because of manufacturing tolerances and differences and because of unavoidable wear and tear however, unequal flow rates and leakage losses will make their appearance, with the result that the volumes of fuel reaching the several cylinders may come to differ from each other. In the embodiment of FIG. 8 it is possible, according to the invention, after reading at the indicating instruments 8 the data on the measuring devices 7, to adjust the pump setting means 84 manually in such a way as to equalize the injection rates.

The setting means 84 may for example take the form of throttling means arranged on the suction side of the pumps. Alternatively, they may comprise racks which are coupled to rod 81 and which serve in known manner to adjust the deliveries from the pumps.

FIG. 9 shows a block diagram of one form of controller usable as the controller 33 in FIG. 3. For simplicity, the example of speed control has been chosen, i.e., that in which the signal delivered on line 16 is representative of engine speed. It will be understood that with suitable modification of the controller, other control variables may also be taken into account. In FIG. 9, the engine 1 is provided with a tachometer 101 and an engine driven pulse generator or distributor 102. From the tachometer 13, a signal line 103 passes into controller 33. From the pulse generator 102, three lines 104 lead to controller 33. Lines 103 and 104 correspond substantially to the signal channel 16 indicated schematically in FIG. 3. The function of the pulse generator 102 is to specify the instant in time at which injection is to begin in each of the cylinders.

The signal supplied at line 103 from tachometer 101 is compared in a control element 105 with the engine speed set value signal on line 15. In the comparator 105 there is generated a control signal, which may for example be a direct-current voltage, representative of the difference between the set value and actual value of engine speed. The signal so generated in element 105 is delivered via line 106 through adders 107 to pulse generators 108. The pulse generators are at the same time connected via signal lines 104 to the pulse generator 102. The output signals of pulse generators 108 are delivered to signal lines 12 to 14 which lead to the several injection valves 9. The adding devices 107 are connected by signal lines 109 to a correction signal generator 110. The generator 110 receives as input signals from lines 30 to 32 the individual cylinder error signals generated in the measuring devices 7, the signals generated there being converted by converters 111 into direct-current voltages for example. The converters 111 are connected by signal lines 112, 113, 114 to the generator 110.

With the engine in operation, the tachometer 102 delivers a signal representative of the instantaneous speed of the engine 1. The pulse generator 102 delivers pulses at the phases of crankshaft rotation when injection is to begin in each of the engine cylinders. The comparator element 105 delivers a signal whose instantaneous magnitude determines, to a first approximation for all cylinders, the duration of the injection process, as a function of the comparison in device 105 of the engine speed set value signal arriving on line 15 and the engine speed actual value signal arriving on line 103. The output signal on the three branches of line 106 has superimposed thereon in the adders 107 the correction signals for the individual cylinders developed in the correction signal generator 110. The corrected signals thus obtained are supplied to the pulse generators 108. Upon arrival there of trigger pulses from the pulse generator 102, generators 108 form control signals of substantially rectangular shape whose durations represent the basic fuel charge signal on line 106, corrected for the individual cylinders in adders 107. In this way the injection valves 9 are actuated in the desired manner at the appropriate times.

In FIG. 9 there is shown the signal line 18 which serves to actuate the pressure regulator 3 according to the comparison above described, made in comparator 105. Line 18 may be omitted if the fuel pressure in the fuel line is kept constant.

FIGS. 10 and 11 show two possible embodiments of the correction signal generator 110 of FIG. 9.

In FIG. 10, the signals from lines 112 to 114 are supplied to control elements 120 and 121, preferably having the form of integral controllers with large time constant. Control elements 120 and 121 deliver to the signal lines 109 for cylinders a and c correction signals dependent on the instantaneous difference between the signals dependent on the instantaneous difference between the signals on lines 113 and 114 and on lines 112 and 114 respectively. The signal on line 13 to cylinder a is in this case not corrected but is rather taken as a basis for comparison. Cylinder a is in this case therefore a master cylinder.

In the embodiment of FIG. 11, the signals on lines 112 to 114 are supplied to control elements 130, 131 and 132. Moreover these signals are added together in an adding circuit 133 and are then applied to a buffer amplifier 134. The buffer 134 has a transmission (amplification) factor of one third. The output signal of the buffer 134, representing a mean of the signals received by it from lines 112 to 114, is applied as a set value signal to each of the control elements 130 to 132. These control elements then take the difference of the two input signals thereto and form an output signal which is applied via signal lines 109 to the several addition elements 107 in FIG. 9.

While the invention has been described hereinabove in terms of a number of presently preferred embodiments of the apparatus thereof, and in terms of the presently preferred practice of the method thereof, the invention itself is not limited thereto, but rather comprehends all modifications of and departures from the apparatus and practice hereinabove described properly falling within the spirit and scope of the appended claims.

Claims

I claim:

1. Fuel injection apparatus for a multicylinder piston-type internal combustion engine comprising means to pump fuel, a separate fuel line connecting the pumping means to each cylinder of the engine, an injector valve in each fuel line, separate means to measure in each fuel line the flow of fuel therethrough and to generate a signal representative thereof, means to compare said signals, and means to adjust the setting of said injector valves in accordance with the result of said comparison.

2. Fuel injector apparatus according to claim 1 wherein said comparison means effect comparison of the signals representative of fuel flow through all of said fuel lines but one against the signal representative of fuel flow through said one fuel line.

3. Fuel injection apparatus according to claim 1 wherein said comparison means develop a signal representative of the average flow of fuel through said fuel lines and wherein said adjusting means adjust the settings of said injector valves in accordance with departures of the fuel flow representative signals of said fuel lines respectively from said average flow representative signal.

4. Fuel injection apparatus according to claim 1 wherein said separate means to measure the flow of fuel comprise volumetric motors and means to detect motion of said motors.