KR102469641B1 - How to control fuel injectors - Google Patents

Abstract

The present invention, in order to inject fuel into the internal combustion engine, a fuel injector 100 including a valve needle 110 movable by an armature 130 engaged with a stopper 120 formed on the valve needle 110 It relates to a method for controlling, in which method, an addition is made between the current supply for the first injection and the current supply for the second injection to the electromagnetic coil 140 interacting with the armature 130, each performed for fuel injection. As a result, current for armature stroke is supplied to the electromagnetic coil 140, which brakes the operation of the armature 130.

Description

How to control fuel injectors

The present invention relates to a method for controlling a fuel injector.

An injection system for an internal combustion engine delivers fuel from a tank to the inside of a combustion chamber of an internal combustion engine. Such injection systems typically include a low pressure system that starts inside the tank and consists of a low pressure pump, fuel filter and lines, and a high pressure system consisting of a high pressure pump, fuel lines, a distributor strip, and an injection valve or fuel injector. Following the low pressure system, injection valves or fuel injectors supply fuel to the combustion chamber of the internal combustion engine in accordance with temporal and spatial demand.

In modern time-controlled injection systems, a control device is responsible for calculating the injection functions, controlling the fuel injector and controlling other control elements for controlling the system and the internal combustion engine.

To open a high-pressure injection valve, for example in a gasoline direct injection system, a magnet is energized, the magnetic force of which moves the valve needle from its seat against the closing spring and the effective fuel pressure in order to open the injection cross section. . In order to keep the current demand as low as possible, the armature is clamped to the valve needle by means of the so-called armature free play. When current is applied, the armature first accelerates and then, after a short stroke, strikes the valve needle. Thus, a mechanical pulse acts in addition to the magnetic force at the time of rising of the valve needle. By doing so, the maximum required magnetic force can be designed lower, and power demand can be reduced.

In internal combustion engines with gasoline direct injection, the high-pressure injection valve is often actuated several times within one combustion cycle in order to ensure time-advantageous injection of fuel into the combustion chamber. In this case, the time interval between two injections in succession, the so-called injection rest period, can vary depending on the operating point.

The limitation of high-pressure injection valves using the principle of armature free play lies within the minimum injection pause period. Subsequent control can normally be activated only when the armature is in proximity to the rest position. If the armature is not in the rest position after the closing process, for example by bounce, there is a risk that the mechanical acceleration will become insufficient to cause injection, ie the risk of lack of continuous injection. This may cause a misfire. Additionally, premature or delayed opening of the valve may result in injection of the wrong amount of fuel.

Therefore, in a fuel injector having an electromagnetic valve and armature free play, it is desirable to shorten the minimum time interval between two injection processes.

According to the invention, a method having the features of patent claim 1 is proposed. Preferred embodiments are the subject of the dependent claims and the detailed description below.

The method according to the invention is used to control a fuel injector comprising a valve needle moveable by an armature engaging a stopper formed on the valve needle for injecting fuel into an internal combustion engine. Normally, in the resting state, the armature is separated from the stopper on the valve needle, that is to say there is so-called armature free play. In this case, in addition between the current supply for the first injection and the current supply for the second injection to the electromagnetic coil interacting with the armature, each performed for fuel injection, an armature to the electromagnetic coil for braking the operation of the armature Stroke current supply is performed.

After the supply of the first injection current ends, the armature bounces mostly several times due to the free play of the armature at another lower stopper, so that the armature is in a position close to the stopper on the valve needle (i.e., not particularly in the rest position). ), the supply of current for the second injection may be started. In this case, the armature may be accelerated insufficiently to raise the valve needle against the force acting on the valve needle, depending on circumstances. However, with the additional current supply for the armature stroke according to the present invention, the bounce of the armature can be weakened because the armature is decelerated while going to the rest position (ie in the closing direction of the valve needle). Current supply for the armature stroke provides a force action in the direction of the armature stroke (ie, in the opening direction of the valve needle without opening the valve needle) which brakes the motion in the direction of the rest position (actuated by the spring). induce With this stabilization of armature operation after closing of the valve needle or fuel injector, a much shorter injection rest period can be used than would be the case without using the method. Another advantage is that the function of the high-pressure injection valve with armature free play is markedly improved due to the small dispersion of the amount of continuous injection even in the case of a short injection rest period.

It should be emphasized that the method according to the invention does not require any structural changes in the fuel injector, but rather can be carried out through suitable control of the same fuel injector.

Preferably, if the additional current supply for armature stroke is continuously used even during a bounce operation in the armature stroke direction, the armature moves up to the stopper by means of the additional current supply for armature stroke. In this way, it is ensured that premature opening of the valve needle and consequently premature fuel injection are not achieved.

Preferably, the supply of current for the first and second injection is performed during one expansion stroke of the internal combustion engine. In particular, the injection effected by the first and second injection current supply, respectively, includes two successive injections, in particular a pilot injection and a main injection or a main injection and a subsequent injection. Therefore, multiple injections are considered necessary during one expansion stroke to increase power and/or increase efficiency in modern internal combustion engines. It should be noted that at this time, a total of two or more injections per expansion stroke may be carried out, in which case the method according to the present invention is preferred for supplying current for injection for any two consecutive injections of one expansion stroke. .

Preferably, the starting point of supplying the current for the additional armature stroke is determined taking into account the period between the end of the current supply for the first injection and the subsequent bounce of the armature at the additional stopper. In particular, the supply of current for the additional armature stroke must be started after said bounce. This period substantially corresponds to the closing delay time. The closing delay time is the time between the end of the control and the closing point at which the release of the fuel delivery ends. The closing delay time can be determined in a simple manner even during normal operation of the internal combustion engine. The closing time may be determined during control of the injector (eg, Controlled Valve operation, CVO). For example, the voltage signal of the electromagnetic coil (the bounce of the armature and valve needle, which is fed back into the current circuit of the valve control via the electromagnetic circuit when closed) can be examined. The operation of the armature can be inferred from the voltage signal. In this way, from the voltage signal, the closing time and ultimately even the closing delay time can be determined. A further optimization of braking is thus achieved.

Since the closing characteristic of one injector can change over time, the starting point of current supply for the armature stroke is preferably determined using an adaptive method and/or depending on the time behavior of the electromagnetic coil. To this end, the start time may be changed regularly and/or when necessary (for example, when the change range of the closing delay time is too large) according to the currently detected closing delay time. Initiation of current supply for the armature stroke in the scope of readjustment, in order to maintain the permanent best functioning of the fuel injector, since a change in the closing delay time may occur, for example, due to consumption or contamination over the life of the fuel injector. An adaptation of the viewpoint can be made, ie the viewpoint can be pulled forward or retarded. To this end, relevant values can be regularly collected and stored, for example by the engine control unit. In this case, adaptation can be carried out as soon as there is, for example, too large a deviation from one optimal value. Consideration of the time behavior (ie inductance) of the electromagnetic coil allows further optimization of the armature damping, since the magnetic field can be optimally formed by starting a current supply matched to it. This also allows an additional current supply to be matched to the switch-off characteristic of the valve. Check-bench measurements are preferred to determine the underlying relationships between the optimal starting point and the aforementioned injector parameters.

Advantageously, between the first and second bounces of the armature at the additional stop formed in the fuel injector, the current supply for the additional armature stroke is started and preferably also ended. This makes it possible to supply the current for the second injection immediately after the second bounce, that is to say the continuous injection, since the second bounce caused by the preceding braking is still very weak. Otherwise, the first bounce must wait longer to allow the valve needle to close the fuel injector normally. Also, during continuous activation, the armature is near the zero position, regardless of when exactly the continuous injection is activated.

The current supply for the additional armature stroke advantageously lasts for a predetermined period, in particular dependent on the start of the current supply for the second injection. Preferably, the supply of current for the additional armature stroke should be terminated before the start of supply of current for the second injection, more preferably before the second bounce as described above. In this way, for example, the braking of the armature can be influenced and optimized as intended.

Preferably, the period of current supply for the armature stroke is determined using an adaptation method and/or depending on the time behavior of the electromagnetic coil. Such an adaptation method can be carried out, for example, by the engine control unit, whereby the necessary parameters can be determined. First of all, a value based on a measurement, in particular a test measurement, can be used for the period of current supply for the armature stroke, which value is readjusted as the fuel injector life elapses, that is to say adapted. That is, the parameters can be changed over the lifetime of the valve, allowing multiple adaptations to be performed. Thus, the additional current supply can be adapted to the changing switch-off characteristics of the valve. In this case, for example, from the value for the delay time of the opening of the valve and the value for the delay time for the closing of the valve and the strength with which the armature and the stopper of the valve needle are fed back into the current circuit of the valve control unit via the electromagnetic circuit, during the bounce and It may be possible to derive a value that correlates with the kinetic energy in the subsequent valve armature. The opening delay time is the time between the start of the control and the opening point at which the flow of fuel or fuel delivery is released. From DE 10 2009 028 650 A1, for example, a method for determining the opening delay time of an electromagnetic injector is known. In this method, the maximum opening period and the maximum control period of the electromagnetic injector in which fuel is not yet deposited are respectively determined. Further, a closing period of the electromagnetic injector is determined for each of the maximum control period and the maximum open period. From these results, the open delay time is determined. The values for the open delay time and the close delay time may change due to, for example, wear or contamination over time. To this end, relevant values can be regularly collected and stored, for example by the engine control unit. In this case, adaptation can be carried out as soon as there is, for example, an excessively large deviation from the optimal value. Consideration of the time behavior (ie inductance) of the electromagnetic coil allows further optimization of the armature damping, since the magnetic field can be configured optimally by means of a current supply period matched to it. This also allows an additional current supply to be matched to the switch-off characteristic of the valve. In order to determine the underlying relationships between the optimum period and the aforementioned injector parameters, test bench measurements are preferred.

Preferably, an additional current supply for the armature stroke, in particular related to the start time, duration and/or amplitude, is carried out depending on fuel pressure and/or temperature and/or fuel characteristics. These variables affect the characteristics of the fuel injector. Thus, better control can be achieved when these variables are taken into account. For example, the current amplitude and/or the exact start of the current supply for the additional armature stroke may vary depending on the fuel pressure or, for example, depending on the fuel viscosity. A higher fuel pressure requires a higher magnetic force to open a valve needle, for example. This can be achieved not only by the current amplitude but also by a modified control time. The temperature affects, on the one hand, the magnetizing properties of the armature and, on the other hand, also the fluid properties of the fuel, for example. Thus, for example, better results can be obtained by considering the temperature at the start and/or duration of the current supply for the additional armature stroke. Since these values change during operation, they can be determined beforehand, for example using a feature map.

In particular, the current supply for the additional armature stroke, related to the start time, duration and/or amplitude, depends on the spring force acting on the valve needle opposite to the direction of movement of the energized armature and/or in the non-energized rest state. This is advantageously carried out according to the distance between the armature and the stopper, and/or according to one or more other parameters specific to the fuel injector, for example geometrical dimensions or mechanical design.

Since these variables also affect the characteristics of the fuel injector, taking them into account can lead to better control. In particular, these values are fixed values that do not change during operation. That is, these values may be set once, for example. The selection of suitable values can be performed, for example, on an inspection table.

Moreover, the aforementioned variables and/or times may particularly preferably also be considered in any combination. In particular, the variable and/or time may mutually influence each other. Determination of these variables and/or times may be performed, for example, by simulation. However, due to variations in individual fuel injectors due to manufacturing, test measurements are also useful. In particular, the optimal parameters and/or times may be different for each fuel injector present in an internal combustion engine.

The calculation unit according to the invention, for example the control device of a motor vehicle, is designed in particular programmatically to perform the method according to the invention.

It is also advantageous to implement the method in the form of software, since this method incurs particularly low costs, especially if the execution-side control device is also used for other tasks and thus exists anyway. Suitable storage media for providing the computer program are, inter alia, diskettes, hard disks, flash memories, EEPROMs, CD-ROMs, DVDs and the like. It is also possible to download programs via a computer network (Internet, intranet, etc.).

Further advantages and improvements of the present invention refer to the detailed description and accompanying drawings.

The foregoing features and the features further described below may be applied within the scope of the present invention not only in the combinations specified herein, but also in other combinations or alone.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is schematically illustrated in the drawings with reference to one embodiment, and is described below with reference to the drawings.

1 is a schematic diagram of a section of a fuel injector with electromagnetic valve and armature free play, capable of carrying out the method according to the invention in one preferred embodiment.
FIG. 2 is a graph showing profiles of an armature stroke and a valve needle stroke executed in a fuel injector having an electromagnetic valve and armature free play when an injection current for fuel injection is supplied.
3 is a graph illustrating a voltage applied to an electromagnetic coil and an armature stroke when controlling a conventional fuel injector.
4 is a graph illustrating a voltage applied to an electromagnetic coil and an armature stroke when controlling a fuel injector according to the present invention.

In FIG. 1 , a section of a fuel injector 100 is schematically shown. The valve needle 110 is provided for the purpose of preventing fuel from reaching the inside of the internal combustion engine from the fuel injector 100 by closing the fuel injector 100 in an idle state. As soon as the valve needle 110 rises, that is, as soon as it moves in the opening direction, fuel is injected into the internal combustion engine.

An electromagnetic coil 140 and an armature 130 are also provided. While the electromagnetic coil 140 is fixedly disposed within the fuel injector 100 , the armature 130 can move in the longitudinal direction of the valve needle 110 . To this end, a hole is provided in the armature 130 having a diameter slightly larger than the diameter of the valve needle 110, for example.

In the resting state, the armature 130 is supported on an additional stopper 160 fixedly connected to the valve needle, which is supported on the armature 130 by, for example, a spring 170 and a spring pot 180. is connected with In the figure shown, the spring 170 is in a state where only the initial stress is applied or expanded. In other words, the spring 170 pulls the armature 130 downward by the initial stress, so that the free play of the armature is maintained. . As soon as current is supplied to the electromagnetic coil 140, the armature 130 moves in the direction of the electromagnetic coil 140 by magnetic force from the rest position. After completion of the current supply, the spring 170 draws the armature normally in the opposite direction to a further stopper 160, which is designed for example as a stopper sleeve. Bounce may be weakened by the initial stress of the spring 170 .

A stopper 120 is formed on the valve needle 110 . At this time, the stopper 120 may be integrally formed with, for example, the valve needle 110, or may be formed as a part fixedly connected to the valve needle 110. At this time, the diameter of the stopper 120 is larger than the diameter of the hole in the armature 130 . In this case, in the rest position of the armature 130, a gap having a width Δh between the upper edge of the armature 130 and the lower edge of the stopper 120, a so-called armature free play, exists.

In addition, a closing spring 150 that presses the valve needle 110 into a valve seat (not shown) is also shown. In addition, in the case of a typical fuel injector 100, due to a corresponding construction, the fuel pressure of the fuel present in the fuel injector 100 and in particular also on the upper surface of the valve needle 110 is also reduced by the spring of the closing spring 150. acts in the direction of the force.

2 schematically shows the profile of the armature stroke (h _M ) and the valve needle stroke (h _V ) in a typical injection process. When injection current is started to be supplied to the electromagnetic coil 140 , the armature 130 moves in the direction of the stopper 120 . After passing the armature free play Δh, the armature 130 follows the valve needle 110 to its upward movement, which leads to the opening of the valve needle 110 and thus the injection process.

For a successful opening process, not only the pulse of the armature at the time when the armature collides with the stopper 120 but also the magnetic force acting at the same time is decisive. After supplying current for injection, the armature descends backward and bounces at the additional stopper 160.

In continuous control immediately after the supply of the current for the second injection, that is, the supply of the current for the first injection, the magnetic force and the pulse are sometimes insufficient to fully open the valve needle, that is, the force acting on the valve needle 110 closes it. It cannot be overcome by spring 150 and fuel pressure. This is because the armature is not at a rest position in some cases after the start of supplying the second injection current, but is rather close to the stopper 120 due to bounce. In this case, the valve needle 110 is not lifted at all or is lifted only in a very decelerated state. This means that no fuel or too little fuel is injected into the internal combustion engine. As a result, for example, undesirable misfires or erroneous injection quantities may be caused.

In FIG. 3 , for conventional fuel injector control, the voltage U applied to the electromagnetic coil over time t and the armature stroke h _M are exemplarily shown in two graphs.

Starting from the left, the current supply for the first injection or the first injection is shown. At this time, at the time point t1, the armature reaches the armature stroke h _M of 0 and bounces for the first time. At time t2, the armature bounces a second time. What can be seen from the voltage U profile is that at the beginning of the period Δt, the voltage rises from a negative value to a value of approximately zero. In this case, the negative value applied beforehand was necessary to cancel the current in the electromagnetic coil of the current supply for the first injection. At this time, the voltage is maintained approximately constant at 0 until the period Δt ends, that is, no current is supplied during the period Δt.

After the period [Delta]t has ended, in particular after the additional period [Delta]t', the second injection current supply is started. Fig. 3 shows voltage profiles with different starting points for supplying the current for the second injection, that is to say with an additional period Δt' of different length, which results in a shift to the right of the positive voltage value in the voltage profile. It can be seen from the point where it is approved. Thus, the period Δt and the additional period Δt' together represent the injection cessation period.

From the relevant profile of the armature stroke, it can be seen that the current supply for the second injection starts when the armature has a relatively large stroke due to the second bounce. At this time, it can be clearly seen that the maximum armature stroke decreases when the supply of the second injection current is started too early, that is, when the injection pause period is too short. The cause is that the magnetic force and pulse not sufficient to raise the valve needle are not reached. This means that in such a case, the electromagnetic valve is not opened at all or is only slightly opened.

In FIG. 4 , two graphs exemplarily show the voltage U applied to the electromagnetic coil and the armature stroke h _M over time t for the fuel injector control according to the present invention.

Also in this embodiment, the current supply for the first injection or the first injection is shown starting from the left. At this time, the armature reaches the zero armature stroke (h _M ) at the time point t1 and bounces for the first time. At time point t2', the armature bounces a second time. What can be seen from the voltage U profile is that the voltage rises from a negative value to a value of approximately zero at the beginning of the period Δt. In this case, the negative value applied beforehand was necessary to cancel the current in the electromagnetic coil of the current supply for the first injection. It can be seen from the additional profile that during the period Δt, unlike the control shown in FIG. 3, an additional current supply for the armature stroke is implemented. This is achieved by applying a positive voltage between times t3 and t4 and a negative voltage between times t5 and t6. Even in this embodiment, a negative voltage value is again needed to cancel the current in the electromagnetic coil.

After the period Δt and the additional period Δt' are finished, the current supply for the second injection is started in this embodiment as well, and in this case again different starting points for supplying the second injection are shown. , this can be seen from the fact that a positive voltage value moves to the right in the voltage profile and is applied.

From the relevant profiles of the armature stroke, it can be seen that the armature stroke after the second bounce is much reduced than without the current supply for the additional armature stroke. Thus, at the start of the supply of the second injection current, the armature has only a relatively small stroke and is located close to its rest position. What can be seen at this time is that the valve needle rises even when the supply of current for the second injection is started early, that is, even when the injection pause period is short. From this, it can be seen that the bounce is weakened by the braking of the armature according to the present invention, as long as a shorter injection pause period than before can be used.

Claims (13)

For controlling a fuel injector 100 including a valve needle 110 movable by an armature 130 engaged with a stopper 120 formed on the valve needle 110 to inject fuel into the internal combustion engine. As a method,
Braking the operation of the armature 130, in addition between the supply of current for the first injection and the supply of current for the second injection to the electromagnetic coil 140 interacting with the armature 130, respectively executed for fuel injection, Current supply for armature stroke to the electromagnetic coil 140 is performed,
The fuel injector control method, wherein the supply of current for the additional armature stroke is started between the first and second bounces of the armature at the additional stopper (160) formed in the fuel injector (100). 2. The fuel injector control method according to claim 1, wherein the supply of current for the first and second injection is performed during one expansion stroke of the internal combustion engine. 2. The fuel injector control method according to claim 1, wherein the injections performed through the first and second injection current supply respectively include two successive injections. delete The method of claim 1, wherein the start point of supplying current for the additional armature stroke is determined in consideration of the period between the end of the first current supply and the subsequent bounce of the armature 130 at the additional stopper 160. How to control fuel injectors. 4. The fuel injector control method according to any one of claims 1 to 3, wherein the supply of additional armature stroke current continues for a predetermined period of time. The fuel injector control method according to any one of claims 1 to 3, wherein the duration of the current supply for the additional armature stroke is determined using an adaptation method and/or depending on the time behavior of the electromagnetic coil. 4. The fuel injector control method according to any one of claims 1 to 3, wherein the start point of the current supply for the additional armature stroke is determined using an adaptation method and/or depending on the time behavior of the electromagnetic coil. 4. A method according to any one of claims 1 to 3, wherein the additional current supply for the armature stroke is performed depending on fuel pressure and/or temperature and/or fuel characteristics. According to any one of claims 1 to 3, the supply of current for the additional armature stroke is based on a spring force acting on the valve needle 110 opposite to the direction of motion of the armature 130 supplied with current, and A fuel injector control method performed according to the distance between the stopper 120 and the armature 130 which is not supplied with current and/or according to another one or more variables specific to the fuel injector 100. . A calculation unit designed to perform the method according to any one of claims 1 to 3. A computer program stored on a machine-readable storage medium which, when executed on a computing unit, causes the computing unit to carry out a method according to any one of claims 1 to 3. A machine-readable storage medium in which the computer program according to claim 12 is stored.

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