EP2376761B1 - Method for operating a fuel injection system of an internal combustion engine - Google Patents

Description

State of the art

The invention relates to a method for operating a fuel system of an internal combustion engine according to the preamble of claim 1. The invention further relates to a computer program, an electrical storage medium and a control and regulating device.

The DE 101 48 218 A1 describes a method of operating a fuel injection system using a quantity control valve. The known quantity control valve is realized as a magnetically actuated by a solenoid solenoid valve with a magnet armature and associated Wegbegrenzungsanschlägen. The known solenoid valve is open in the energized state of the coil. However, known from the market are also such quantity control valves, which are closed in the de-energized state of the solenoid. In the latter case, to open the quantity control valve, the solenoid coil is driven with a constant voltage or a pulsed voltage (pulse width modulation - "PWM"), whereby the current in the magnetic coil increases in a characteristic manner. After the voltage has been switched off, the current again drops in a characteristic manner, as a result of which the quantity control valve closes (in the case of the normally closed valve) or opens (in the case of the normally open valve).

At the in the DE 101 48 218 A1 The normally closed valve shown in FIG. 1 prevents the armature from striking the stop at full speed during the opening movement of the quantity control valve, which could lead to a significant noise development Electromagnetic actuator shortly before the end of the opening movement energized again like a pulse. By this current pulse, a braking force is applied to the armature, before it contacts the stop. The braking force reduces the speed, which reduces the impact noise.

Disclosure of the invention

The object of the present invention is to provide a method for operating a fuel injection system of an internal combustion engine, in which the quietest possible operation of the fuel injection system is achieved.

This object is achieved by a method having the features of claim 1. Advantageous developments of the method according to the invention are specified in subclaims. Further possible solutions are also mentioned in the independent patent claims. For the invention important features can be found also in the following description and in the drawing, these features may be essential both in isolation and in different combinations for the invention, without being explicitly pointed out.

According to the invention it has been found that the magnetic actuator can differ from one copy to another. The reason for this is on the one hand production-related tolerances, but also environmental parameters that can differ from one fuel injection system to another and above all from an operating situation of a fuel injection system to another. In particular, it has been recognized that a distinction can be made between fast-absorbing, that is to say efficient, electromagnetic actuators and slow-moving, that is, rather inefficient electromagnetic actuators. Because of these variances, it has so far been possible that the braking pulse was not optimal. This risk is excluded or at least significantly reduced with the present invention.

Overall, it has been found to be advantageous for noise reduction, when in an electromagnetic actuator with higher efficiency of the brake pulse is later and / or takes less and / or less pronounced than in an electromagnetic actuator with lower efficiency.

In addition, it has been found that the braking pulse, for example, from a supply voltage of a voltage source and / or a temperature in particular a component of the fuel injection system or the internal combustion engine can depend. This is also taken into account by the invention, for example via a characteristic map, which can be determined for a nominal quantity control valve as functions of a nominal, temperature-dependent resistance and the voltage of a voltage source, for example a vehicle battery. The reason for the consideration of the temperature is that the electrical resistances of electrical lines, with which the quantity control valve is connected, for example, to an output stage of a control unit, depends on the current temperature of these electrical lines. This can be taken into account by the method according to the invention.

The present invention therefore makes it possible to reduce the impact speed of the valve element on a stop and thereby the noise during operation of the quantity control valve. By using an adaptation method, this succeeds for individual quantity control valves, whereby the demands on the manufacturing tolerance can be reduced. This can reduce the cost of manufacturing the fuel injection system. In a repeated application of the method according to the invention over the life of the high-pressure pump also wear and / or aging-related effects can be compensated, whereby a robust operation over the entire life of the quantity control valve is achieved. In addition to reducing noise emissions, the scattering of the noise, measured over a given sample size, is also minimized. Specified noise limits can therefore be maintained more reliably. By reducing the velocity of the stop, the load on the stops is reduced. This reduces the corresponding load collective, so that lower wear and strength requirements can be made of the quantity control valve. This reduces the costs. In addition, the risk of failure is reduced. Additional hardware for the realization of the method according to the invention is not required, so far there are no additional unit costs.

The parameters of the braking pulse are particularly well suited: start of the braking pulse, duration of a PWM phase ("PWM" = pulse width modulation) or a current-controlled phase of the braking pulse, duration one before the first PWM phase occurring pull-in pulse, duty cycle or current level during a holding phase of the braking pulse, duty cycle or current level at the end of a holding phase of the braking pulse.

It also has an effect on the braking pulse when the duty cycle or the current level at the end of a holding phase of the braking pulse is increased. This can be achieved in a discrete output stage by changing the duty cycle, in a current-controlled output stage by controlling the current level. Likewise, output stages are conceivable in which current-controlled phases and PWM-controlled phases alternate. The use of these intervention options for the output of an adapted braking pulse can be carried out in sections.

To detect whether the solenoid valve just does not close or just opens, a deviation of an actual pressure in the fuel rail can be used by a target pressure. This is based, for example, in a normally open quantity control valve, the idea that in the adaptation process, when the energization of the electromagnetic actuator has been lowered so far that the quantity control valve does not close anymore, a pressure drop or even pressure breakdown occurs in the fuel rail then the high-pressure pump promotes no more fuel.

The parameter of a braking pulse may also be the form of the braking pulse, which is defined in a simple manner by following several PWM phases, several tightening pulse phases without PWM, current-controlled phases, defined step deletions and / or Zener deletions.

Another measure for reducing the noise emissions is that an energized holding phase of the electromagnetic

Although actuator begins during a delivery stroke, but is terminated shortly after the end of the delivery stroke. As a result, tolerances of the movement of a piston of the high-pressure pump and thus a position of the top dead center between the delivery and suction phases are reduced.

In order to avoid a non-round sound impression by stochastic effects when using a discrete output stage, ie a control of the electromagnetic actuator with pulse-width modulation, it is proposed that a holding phase is terminated at a defined, for example, falling PWM edge. This initiates the beginning of a quenching of the coil current at a defined current level. The valve element therefore drops in a reproducible manner, whereby a variation of the effect of the braking pulse is avoided.

Figur 1

eine schematische Darstellung eines Kraftstoffeinspritzsystems einer Brennkraftmaschine mit einer Hochdruckpumpe und einem Mengensteuerventil;

Figur 2

einen teilweisen Schnitt durch das Mengensteuerventil von Figur 1;

Figur 3

eine schematische Darstellung verschiedener Funktionszustände der Hochdruckpumpe und des Mengensteuerventils von Figur 1 mit einem zugehörigen Zeitdiagramm;

Figur 4

drei Diagramme, in denen eine Ansteuerspannung, eine Bestromung einer Magnetspule, und ein Hub eines Ventilelements des Mengensteuerventils von Figur 1 über der Zeit aufgetragen sind, bei Durchführung eines Adaptionsverfahrens;

Figur 5

ein Diagramm, in dem ein Verlauf einer Bestromung des Mengensteuerventils von Figur 1 über der Zeit bei Realisierung eines Bremsimpulses aufgetragen ist;

Figur 6

ein Diagramm ähnlich zu Figur 5, bei einer Variante des Stromverlaufs; und

Figur 7

ein Flussdiagramm eines Verfahrens zum Betreiben des Kraftstoffeinspritzsystems von Figur 1.

Hereinafter, embodiments of the invention will be explained in more detail with reference to the accompanying drawings. In the drawing show:

FIG. 1

a schematic representation of a fuel injection system of an internal combustion engine with a high-pressure pump and a quantity control valve;

FIG. 2

a partial section through the quantity control valve of FIG. 1 ;

FIG. 3

a schematic representation of various functional states of the high pressure pump and the flow control valve of FIG. 1 with an associated time chart;

FIG. 4

three diagrams in which a drive voltage, a current supply to a solenoid coil, and a stroke of a valve element of the quantity control valve of FIG. 1 plotted over time when performing an adaptation method;

FIG. 5

a diagram in which a course of energization of the quantity control valve of FIG. 1 is plotted over time upon realization of a braking pulse;

FIG. 6

a diagram similar to FIG. 5 in a variant of the current profile; and

FIG. 7

a flowchart of a method for operating the fuel injection system of FIG. 1 ,

A fuel injection system contributes in FIG. 1 Overall, the reference numeral 10. It includes an electric fuel pump 12, is conveyed with the fuel from a fuel tank 14 to a high-pressure pump 16. The high-pressure pump 16 compresses the fuel to a very high pressure and promotes it further into a fuel rail 18. To this several injectors 20 are connected, which inject the fuel in them associated combustion chambers. The pressure in the fuel rail 18 is detected by a pressure sensor 22.

In the high-pressure pump 16 is a piston pump with a delivery piston 24, which can be offset by a camshaft, not shown, in a reciprocating motion (double arrow 26). The delivery piston 24 defines a delivery chamber 28, which can be connected via a quantity control valve 30 to the outlet of the electric fuel pump 12. Via an outlet valve 32, the delivery chamber 28 can also be connected to the fuel rail 18.

The quantity control valve 30 comprises an electromagnetic actuator 34 which operates in the energized state against the force of a spring 36. When de-energized, the quantity control valve 30 is open, in the energized state, it has the function of a normal inlet check valve. The exact structure of the quantity control valve 30 goes out FIG. 2 out:

The quantity control valve 30 comprises a disc-shaped valve element 38, which is acted upon by a valve spring 40 against a valve seat 42. The latter three elements form the above-mentioned inlet check valve.

The electromagnetic actuating device 34 comprises a magnetic coil 44 which cooperates with a magnetic armature 46 of an actuating tappet 48. The spring 36 acts on the actuating plunger 48 in the currentless solenoid 44 against the valve element 38 and forces it to its open position. The corresponding end position of the actuating plunger 48 is defined by a first stop 50. When the solenoid is energized, the actuating plunger 48 is moved against the force of the spring 36 away from the valve element 38 against a second stop 52.

The high-pressure pump 16 and the quantity control valve 30 operate as follows (see FIG. 3 ):

In FIG. 3 At the top is a stroke of the piston 34 and below an energization of the solenoid 44 is plotted over time. In addition, the high pressure pump 16 is shown schematically in various operating conditions. During a suction stroke (left illustration in FIG. 3 ), the solenoid 44 is de-energized, whereby the actuating plunger 48 is pressed by the spring 36 against the valve element 38 and moves it to its open position. In this way, fuel can flow from the electric fuel pump 12 into the delivery chamber 28. After reaching the bottom dead center UT of the delivery stroke of the delivery piston 24 begins. This is in FIG. 3 shown in the middle. The solenoid 44 is still de-energized, whereby the mass control valve 30 is further forced to open. The fuel is discharged from the delivery piston 24 via the open quantity control valve 30 to the electric fuel pump 12. The exhaust valve 32 remains closed. A promotion in the fuel rail 18 does not take place. At a time t ₁ , the solenoid coil 44 is energized, whereby the actuating plunger 48 is pulled away from the valve element 38. It should be noted at this point that in FIG. 3 the course of the energization of the magnetic coil 44 is shown only schematically. As will be explained below, the actual coil current is not constant, but may drop due to mutual induction effects. In addition, in the case of a pulse-width-modulated drive voltage, the coil current is wave-shaped or jagged.

Due to the pressure in the delivery chamber 28, the valve element 38 applies to the valve seat 42, the quantity control valve 30 is thus closed. Now, a pressure can build up in the delivery chamber 28, which leads to an opening of the exhaust valve 32 and to a delivery into the fuel rail 18. This is in FIG. 3 all shown on the right. Shortly after reaching the top dead center OT of the delivery piston 24, the energization of the solenoid 44 is terminated, whereby the quantity control valve 30 returns to its forced open position.

By varying the time t ₁ , the amount of fuel delivered by the high-pressure pump 16 to the fuel rail 18 is influenced. The time t ₁ is determined by a control and regulating device 54 (FIG. FIG. 1 ) determined so that an actual pressure in the fuel rail 18 as closely as possible corresponds to a target pressure. For this purpose, 54 signals supplied by the pressure sensor 22 are processed in the control and regulating device.

When stopping the energization of the solenoid 44, the actuating plunger 48 is again moved against the first stop 50. In order to reduce the impact velocity at the first stop 50, a braking pulse 56 is generated, by which the speed of movement of the actuating plunger 48 is reduced shortly before impinging on the first stop 50.

At the in FIG. 1 Fuel injection system 10 shown at least depends on the efficiency of the electromagnetic actuator 34 at least one parameter of the braking pulse 56. This efficiency is determined by an adaptation method which will now be described with reference to FIG. 4 is explained. Thereafter, after a first cycle of the high pressure pump 16 (a working cycle consists of a suction stroke and a delivery stroke) a duty cycle of a pulse width modulated drive voltage after a first so-called "suit pulse" 58 is set to a first value, in which it is ensured that the actuating plunger 48 from the valve element 38 is moved away. The corresponding course of the coil current is in FIG. 4 designated 60a. It can be seen that due to the movement of the actuating tappet 48 and the magnet armature 46 coupled thereto in the magnet coil 44, a mutual induction is produced, which leads to a reduction of the effective coil current. The movement of the actuating plunger 48 and the valve element 38, so their stroke H is in this case in FIG. 4 designated 62a.

In a subsequent cycle, the duty cycle is adjusted so that a lower effective current supply of the solenoid coil 44 results, corresponding to a curve 60b in FIG. 4 , As a result, there is a delayed movement of the actuating plunger 48 and the valve element 38, corresponding to the curve 62b. The duty cycle is successively changed further, so that the effective coil current decreases further. In a coil current shown by way of example as a curve 60c, corresponding to a "limit duty cycle", the actuation tappet 48 is no longer sufficiently moved away from the valve element 38, ie the quantity control valve 30 remains open (curve 62c). There is thus no promotion of fuel in the fuel rail 18 instead. This in turn leads due to the fuel flow through the injectors 20 from the fuel rail 18 to a strong pressure drop in the fuel rail 18, so a strong and sudden deviation of the actual pressure in the fuel rail 18 from the target pressure, which is detected by the control and regulating device 54. With this adaptation method, therefore, it is possible to determine that duty cycle at which the quantity control valve 30 no longer or just just opens.

This limit duty cycle, which can also be referred to as the "final value", is used to characterize the efficiency of the electromagnetic actuator 34. Namely, a mass control valve 30 having a more efficient electromagnetic actuator 34 has a lower final value than a mass control valve 30 having a more inefficient electromagnetic actuator 34. The thus determined efficiency of the individual electromagnetic actuator 34 is now used to parameterize the braking pulse 56. In addition, the level of a supply voltage, for example, a battery of a motor vehicle, in which the internal combustion engine is installed, and a temperature, for example, of the fuel used for the parameterization of the braking pulse. The parameter of the braking pulse 56 may be a start of the braking pulse, a duration of a pulse-width modulated phase or (in the case of a current-controlled output stage) the duration of a current-controlled phase of the braking pulse 56. The duration of the starting pulse 58 occurring before the pulse-width-modulated phase can also be such a parameter. Further, a duty cycle or a current level during the holding phase before the braking pulse 56, and / or a duty cycle or a current level at the end of the holding phase before the braking pulse 56th

Now it will open FIG. 5 Referring to FIG. 5, a coil current 60 is plotted against time, including the brake pulse 56. A hold phase 64 is seen extending into the suction phase above top dead center. It can be seen that the holding phase 64 is terminated on a falling edge of the pulse-width-modulated voltage signal. The current initially drops freely ("freewheeling"), before a rapid quenching is performed by applying a countercurrent. Freewheeling and rapid quenching are within a period 66, which elapses from the end of the holding phase until the beginning of the braking pulse 56. The braking pulse 56 itself is in turn generated a pulse width modulated signal whose duration in FIG. 5 designated 68. How out FIG. 6 can be seen, at the end of the hold phase 64, the duty cycle can be changed so that an increase of the effective coil current 60 results. The shape of the brake pulse 56 may be defined by following several pulse width modulated phases, pull pulse phases without pulse width modulation, current controlled phases, defined step cancellations, and / or Zener clearances. Overall, for noise reduction, the brake pulse 56 will be applied to an electromagnetic actuator 34 of higher efficiency sooner and / or shorter and / or less pronounced than an electromagnetic actuator 34 of lower efficiency.

In FIG. 7 A method of operating the fuel injection system 10 is illustrated. In FIG. 70, based on the signal of the pressure sensor 22, the actual pressure in the fuel rail 18 is compared with the target pressure. With the above related to FIG. 4 72, the final value of the duty cycle and, therefrom, a variable characterizing the efficiency of the electromagnetic actuator 34 are determined. By using such a duty ratio, which just closes the flow control valve 30, a reduced speed when striking the actuating plunger 48 on the second stop 52 and thereby a noise reduction is achieved (block 74). 76, the voltage of the vehicle battery and the temperature of the fuel are detected. These sensed values become 78 in conjunction with the efficiency of the electromagnetic actuator 34 for parameterizing the brake pulse 56 as determined by the method of FIG. 72 used. This results in 80 a noise reduction when hitting the actuating plunger 48 on the first stop 50th

In one embodiment, not shown, a braking pulse is generated only below a certain speed of a crankshaft of the internal combustion engine or a drive shaft of the high-pressure pump 16. In a further embodiment, not shown, the braking pulse is generated above such a speed, it takes place above this speed but no adjustment of the braking pulse more.

Claims (10)

1. Method for operating a fuel injection system (10) of an internal combustion engine, in which method fuel is fed into a fuel rail (18) via a highpressure pump (16), and in which method the quantity of fed fuel is influenced by a solenoid control valve which is actuated by an electromagnetic activation device (34), wherein at least one parameter of a braking pulse (56) of the electromagnetic activation device (34) depends on the efficiency of the electromagnetic activation device and/or on the voltage of a voltage source and/or on a temperature, in particular of a component of the fuel injection system (10) or of the internal combustion engine, characterized in that when there is an electromagnetic activation device (34) with a relatively high efficiency the braking pulse (56) occurs later and/or lasts for a shorter time and/or is less pronounced than when there is an electromagnetic activation device (34) with a relatively low efficiency.
2. Method according to Claim 1, characterized in that in an adaption method energy which is fed to the electromagnetic activation device is changed from a starting value successively to an end value which is such that closing or opening of the solenoid control valve (30) is no longer detected at least indirectly or is just detected, and in that the end value or a variable which is based thereon and has the purpose of characterizing the efficiency of the electromagnetic activation device (34) is used.
3. Method according to one of the preceding claims, characterized in that the parameter is a start of the braking pulse, a duration of a PWM phase or of a current-regulated phase of the braking pulse, a duration of an attraction pulse which takes place before the first PWM phase, a pulse duty factor or a level of current during a holding phase before the braking pulse and/or a pulse duty factor or a current level at the end of a holding phase before the braking pulse.
4. Method according to one of the preceding claims, characterized in that opening or closing of the solenoid valve (30) is detected by monitoring a deviation of an actual pressure in the fuel rail (18) from a setpoint pressure.
5. Method according to one of the preceding claims, characterized in that the shape of the braking pulse (56) is defined by sequences of a plurality of PWM phases, attraction pulse phases without PWM, current-regulated phases, defined stepped extinctions and/or Zener extinctions.
6. Method according to one of the preceding claims, characterized in that an energized holding phase (64) of the electromagnetic activation device (34) starts during a delivery stroke and is ended after the end of the delivery stroke.
7. Method according to one of the preceding claims, characterized in that in the case of actuation with PWM a holding phase (64) is ended at a defined, for example falling, PWM signal edge.
8. Computer program, characterized in that it is programmed for application in a method according to one of the preceding claims.
9. Electrical storage medium for an open-loop and/or closed-loop control device (54) of a fuel injection system (10), characterized in that a computer program for application in a method of Claims 1 to 8 is stored on said storage medium.
10. Open-loop and/or closed-loop control device (54) for a fuel injection system (10), characterized in that said device is programmed for application in a method according to one of Claims 1 to 8.

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