EP2986835B1 - Method and device for controlling a volume regulation valve - Google Patents

Description

State of the art

The invention relates to a method for controlling a quantity control valve of a high-pressure pump 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 for operating a fuel injection system using a quantity control valve. The known quantity control valve is implemented as a solenoid valve electromagnetically actuated by a solenoid coil with a magnet armature and associated travel limit stops. Such quantity control valves are known on the market which are closed when the solenoid coil is de-energized. In this case, to open the quantity control valve, the solenoid coil is controlled with a constant voltage or a clocked voltage (pulse width modulation - "PWM"), whereby the current in the solenoid coil increases in a characteristic manner. After the voltage is switched off, the current drops again in a characteristic manner, whereby the quantity control valve closes. Solenoid valves are also known which are open when the coil is energized. The procedure for these solenoid valves is similar, whereby the solenoid valve opens when the voltage is switched off and the current drops in a characteristic manner.

To be able to DE 101 48 218 A1 To prevent the armature from hitting the stop during the opening movement of the quantity control valve at full speed, which could lead to significant noise, the electromagnetic The actuating device is energized again in a pulsed manner shortly before the end of the opening movement. This current pulse exerts a braking force on the armature before it even comes into contact with the stop. The braking force reduces the speed, which reduces the impact noise.

In modern direct-injection engine systems with demand-controlled fuel delivery, a high-pressure pump is used to generate the necessary fuel pressure. The high-pressure pump is operated in a quantity-controlled manner; the pump delivery rate can be set from 0 to 100% using a quantity control valve (MSV). The control of this quantity control valve is particularly important because the switching process of the MSV must take place in a very short time and despite high magnetic forces due to the high speed and the associated high control frequency, without the stroke-to-stroke fluctuations and thus the delivery rate fluctuations becoming too great. This would lead to poor rail pressure quality. On the other hand, at low engine speeds, very high demands are placed on the noise development of the high-pressure pump. For this reason, numerous control concepts have already been developed to reduce the impact dynamics and thus reduce the acoustic level. Both the pulling movement and the falling movement of the switching magnet are slowed down.

From the DE 10 2009 046 825 A1 A control concept for a quantity control valve is described, which is also called "Current Soft Stop" (CSS).

Normally, the quantity control valve is kept closed beyond the top dead center by the pressure in the delivery chamber of the high-pressure pump. When the delivery chamber pressure drops, the quantity control valve falls back to its original, currentless open position, driven by spring force and without braking. In the CSS process, the quantity control valve is supplied with a holding current beyond the top dead center, so that the MSV does not drop directly. Only after the pressure in the delivery chamber has dropped is the current reduced in a characteristic way, so that the quantity control valve drops during this low current supply and falls back to the currentless open position. The movement is slowed down by counter-induction and the current through the quantity control valve, and the impact on the stop occurs much more slowly and therefore more quietly. The holding current should be known as precisely as possible so that the currents for holding and starting the movement can be set as precisely as possible. The current supply must end before the following bottom dead center so that the next conveying process is not disrupted.

The problem is that if the current is too low, the CSS process only brings about slight acoustic improvements, while if the current is too high, there is no improvement or it can even lead to an acoustic deterioration and an increase in rail pressure. This is because if the current is too high, the quantity control valve remains closed and does not open.

Since the variation between individual units must be taken into account when setting the current, the effect would be limited under these conditions, since the current is usually set in such a way that the quantity control valve opens safely. This means that a current that is too low would be selected. At this low current, there may only be a slight improvement in the acoustics.

From the WO 2010/066663 A1 A method is known in which an adoption process is used in which a deviation of an actual pressure in the fuel rail from a target pressure can be used. The current supply disclosed there in connection with the adaptation ends after the top dead center and well before the bottom dead center of the high-pressure pump. The current supply to the electromagnetic actuating device is reduced so far that the quantity control valve no longer closes and therefore a pressure drop or even a pressure collapse occurs in the fuel rail.

Furthermore, the DE 10 2008 054 702 A1 A solenoid valve is already known which is designed as a normally open solenoid valve. The coil is energized in a phase which begins approximately in the middle between a bottom dead center and a top dead center and ends at the top dead center. It is intended that in the adaptation method disclosed therein the aforementioned current in the coil is reduced in order to detect or not detect a drop in pressure in the course of a large number of successive reductions. in this case, the emission of audible sound that occurs when the solenoid valve closes when the internal combustion engine is operating is at least partially reduced. The coil of the solenoid valve is energized according to a target value for the current in the coil in order to close it to supply fuel to the high-pressure pump. When the solenoid valve closes, the target value for the current in the coil is reduced from a predetermined first current target value to a predetermined second current target value in such a way that the emission of audible sound that occurs when the solenoid valve closes when the internal combustion engine is operating is at least partially reduced.

disclosure of the invention

The invention relates to a quantity control valve with an electromagnetic actuating device which, when actuated with a first actuation value for the holding current, assumes a closed state and the actuation with a second actuation value enables the quantity control valve to assume an open state.

By determining a limiting holding current at which the quantity control valve remains in its closed state at the bottom dead center of the high-pressure pump, a significantly improved control is possible, with the acoustic behavior being significantly improved.

Since the properties of the quantity control valve vary from model to model, an effective reduction in the impact noise is achieved if model properties, such as the limit holding current, are taken into account during the current supply.

This limit holding current is determined by setting a control value for the holding current in one step, at which the quantity control valve opens when the pressure has dropped, and the current supply to the quantity control valve is extended beyond the bottom dead center of the high-pressure pump, whereby no pressure increase occurs in the fuel rail, and the holding current is successively incremented from delivery to delivery and the current supply is extended beyond the bottom dead center of the high-pressure pump with each delivery, wherein, when the quantity control valve remains closed during a delivery stroke which begins after the bottom dead centre of the high pressure pump and a pressure increase occurs, a current value before the last increment is used as a limit holding current, wherein the limit holding current is determined based on the control signal at which the pressure increase occurs by using the current value before a last increment as a limit holding current.

Through the control and adaptation according to the invention, the current level, or the current supply to the quantity control valve pre-controlled by a PWM signal, is adapted to the specimen tolerances in such a way that the CSS method for acoustic improvement functions optimally.

It is particularly advantageous if the limit holding current is determined based on a fuel pressure signal. Since the fuel pressure signal is evaluated, no further sensors are required. Furthermore, this signal is available with sufficient accuracy.

A pressure increase can be easily detected if the current supply to the quantity control valve is extended beyond the bottom dead center.

• Figur 1 eine schematische Darstellung eines Kraftstoffeinspritzsystems einer Brennkraftmaschine mit einer Hochdruckpumpe und einem Mengensteuerventil;
• Figur 2 eine schematische Darstellung des Zusammenhangs zwischen dem Ansteuersignal und dem Zustand des Mengensteuerventils;
• Figur 3 eine zweite schematische Darstellung des zeitlichen Verlaufs des Ansteuersignals und des zeitlichen Verlaufs des Zustands des Mengensteuerventils;
• Figur 4 ein Flussdiagramm zur Verdeutlichung der erfindungsgemäßen Vorgehensweise.

Embodiments of the invention are explained in more detail below with reference to the accompanying drawings. In the drawings:

• Figure 1 a schematic representation of a fuel injection system of an internal combustion engine with a high-pressure pump and a quantity control valve;
• Figure 2 a schematic representation of the relationship between the control signal and the state of the quantity control valve;
• Figure 3 a second schematic representation of the temporal course of the control signal and the temporal course of the state of the quantity control valve;
• Figure 4 a flow chart to illustrate the procedure according to the invention.

A fuel injection system contributes to Figure 1 overall the reference number 10. It comprises an electric fuel pump 12, with which fuel is pumped 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 pumps it further into a fuel rail 18. Several injectors 20 are connected to this, which inject the fuel into the combustion chambers assigned to them. The pressure in the fuel rail 18 is detected by a pressure sensor 22.

The high-pressure pump 16 is a piston pump with a delivery piston 24, which can be set in a back and forth movement (double arrow 26) by a camshaft (not shown). The delivery piston 24 delimits a delivery chamber 28, which can be connected to the outlet of the electric fuel pump 12 via a quantity control valve 30. The delivery chamber 28 can also be connected to the fuel rail 18 via an outlet valve 32.

The quantity control valve 30 comprises, for example, an electromagnetic actuating device 34 which, when energized, works against the force of a spring 36. In the form of the exemplary embodiment, the quantity control valve 30 is open when de-energized; when energized, it has the function of a normal inlet check valve.

The high pressure pump 16 and the quantity control valve 30 operate as follows (see Figure 2 ):
In Figure 2 At the top, a stroke of the piston 34 and below it a control signal are plotted over time. The control signal is designated with the reference symbol "A". The value of the control signal is between a first control value, which is in Figure 2 marked with "0" and a second control value, which is Figure 2 is marked with "1". For example, the first control value corresponds to the de-energized state of the electromagnetic

Actuating device 34 and the second value the energized state. In the following, this embodiment is assumed.

In addition, the high-pressure pump 16 is shown schematically in various operating states. During a suction stroke (left illustration in Figure 2 ), the solenoid coil 44 is de-energized, whereby the actuating plunger 48 is pressed against the valve element 38 by the spring 36 and moves this into 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, the delivery stroke of the delivery piston 24 begins. This is in Figure 2 shown in the middle. The magnetic coil 44 is still de-energized, as a result of which the quantity control valve 30 is still forcibly open. The fuel is expelled from the feed piston 24 via the open quantity control valve 30 to the electric fuel pump 12. The outlet valve 32 remains closed. Fuel is not fed into the fuel rail 18. At a time t1, the magnetic coil 44 is energized, as a result of which the actuating plunger 48 is pulled away from the valve element 38. It should be noted at this point that the course of the energization of the magnetic coil 44 is only shown schematically in Figure 2. It should be noted that the actual coil current is not constant, but due to mutual induction effects may simulate the course of typical transient processes. With a pulse-width modulated control voltage, the coil current is also wave-like or spike-like.

By varying the time t1, the amount of fuel delivered by the high-pressure pump 16 to the fuel rail 18 is influenced. The time t1 is controlled by a control and regulating device 54 ( Figure 1 ) so that an actual pressure in the fuel rail 18 corresponds as closely as possible to a target pressure. For this purpose, signals supplied by the pressure sensor 22 are processed in the control and regulating device 54.

Due to the pressure in the delivery chamber 28, the valve element 38 rests against the valve seat 42, thus the quantity control valve 30 is closed. Pressure can now build up in the delivery chamber 28, which leads to the outlet valve 32 opening and to a delivery into the fuel rail 18. This is in Figure 2 quite shown on the right. Shortly after reaching the top dead center TDC of the delivery piston 24, the current supply to the solenoid coil 44 is terminated, whereby the quantity control valve 30 returns to its forced open position.

When the current supply to the magnetic coil 44 is terminated, the actuating plunger 48 is moved against a first stop 50. In order to reduce the impact speed at the first stop 50, a temporarily falling signal curve 56 is generated, by which the movement speed of the actuating plunger 48 is reduced before it hits the first stop 50. During a second falling signal curve 58, the control signal is brought to the first control value. This second falling signal curve 58 can be provided, for example, by a rapid extinguishing of the coil current of the electromagnetic actuating device 34.

Figure 3 shows an exemplary time profile 100 of the control signal designated "A" and the time profile 102 of the state of the quantity control valve 30 designated "Z". At time t1, the value of the control signal is increased from the second control value 64 to the first control value 66. As a result, the quantity control valve 30 changes from the open state 60 to the closed state 62 and closes at time 104. During a holding phase 106, the quantity control valve 30 remains closed. Due to the pressure in the delivery chamber 28, which keeps the quantity control valve 30 closed, the control signal can assume the second control value 64 during a period 108, i.e., be de-energized, for example. In a further variant of the method, the holding current can also be maintained during the period 108 by applying the first control value. Before reaching the top dead center 120 of the delivery piston 24 or before opening 122 of the outlet valve 32, the value of the control signal is raised again to the first control value 66. Starting at time 82, control is again carried out. In order to significantly reduce noise emissions, according to the invention the value of the control signal is specified at the time at which the pressure in the delivery chamber 28 has dropped so far that it no longer holds the quantity control valve 30 in the closed state 62, starting from a limit holding current.

The limit holding current is the holding current at which the quantity control valve remains in its closed state after a previous current supply. If a higher current than the limit holding current is selected, the quantity control valve remains closed. If a lower current is selected, the quantity control valve opens.

In order to detect whether the current currently being output is above or below the limit holding current, the current is extended beyond the bottom dead center of the high-pressure pump. If the quantity control valve is still activated because the current is above the limit holding current, the high-pressure pump is fully discharged. This full discharge can be easily detected by the pressure increase in the rail using the rail pressure sensor. If the limit holding current is not reached, there is no discharge and no pressure increase.

In the method according to the invention, starting from a current level at which the quantity control valve opens reliably, the extended current is gradually increased from delivery to delivery until a pressure increase is detected. In this way, the limit holding current associated with the quantity control valve example currently present is recorded under the respective boundary conditions.

Alternatively, it can also be provided that the extended flow, starting from a flow level at which the quantity control valve remains closed, is successively reduced from delivery to delivery until a pressure drop is detected.

An embodiment of the procedure according to the invention is exemplified by the Figure 4 described.

The adaptation process starts in a first step 300. The subsequent query 305 checks whether the activation conditions for the adaptation are met.

The switch-on conditions should ensure the most uniform boundary conditions possible for the adaptation process. Therefore, the adaptation is only carried out in a certain speed range, vehicle speed range, battery voltage range, rail pressure range, load range, temperature range, preferably when the engine is idling but also when driving at a steady slow speed. The target pressure specification for the rail pressure must also not change.

In the subsequent step 310, a starting value for the holding current is set. Furthermore, the current supply is extended beyond the bottom dead center of the high-pressure pump. This ensures that the quantity control valve remains closed with appropriate current supply until the next delivery stroke, which begins after the bottom dead center. If the quantity control valve is supplied with a current value above the limit holding current, it remains closed and pressure builds up. If the quantity control valve is supplied with a current value below the limit holding current, the quantity control valve can open when the pressure has dropped. The starting value is preferably specified so that the quantity control valve opens when the pressure has dropped.

In step 315, the current value is incremented by a certain value. In the subsequent step 320, the rail pressure in the high-pressure area after the high-pressure pump is recorded.

The subsequent query 325 checks whether the rail pressure has increased. For example, it is checked whether the gradient of the rail pressure is greater than a threshold value. Or it is checked whether the rail pressure has increased by more than a threshold value since the last recording.

If this is not the case, i.e. there is no increase in pressure, the current value is incremented by a certain value in step 315. If a rail pressure increase is detected in step 325, step 330 follows.

The adaptation ends in step 330. The current value, or the current value before the last increment, is used as the limit holding current. Alternatively, a value calculated from the two values, in particular the average of these two values can be used as the limit holding current.

In step 335, the parameters for the CSS current supply are determined, starting from the limit holding current. Furthermore, the duration of the current supply is reset to the normal value.

The method ends in the subsequent step 340.

This limit holding current is then used for the correct CSS control by calculating or correcting the current supply of the CSS process depending on this detected limit holding current.

The holding current before the CSS phase, which corresponds to the period before the discharge chamber pressure drops, is selected with a suitable increase compared to the determined limit holding current so that the quantity control valve is reliably kept closed. The current value for the desired drop to the open position of the quantity control valve is selected, for example, with a current reduced by a suitable amount compared to the determined limit holding current. This is intended on the one hand to ensure that the quantity control valve is reliably held until the start of movement is to be initiated and on the other hand to achieve the maximum braking effect of the current during the movement of the quantity control valve. In this phase, the current is selected to be just below the holding current required for the specimen.

The characterization of the respective quantity control valve specimen obtained with the adaptation method can not only be used to improve the CSS method. An additional use would be to determine the limit holding current in the context of normal control in order to reduce the effective current level and the power loss.

Claims (6)

1. Method for actuating a quantity control valve (30) of a high-pressure pump which delivers compressed fuel to a fuel rail (18) and a pressure in the fuel rail (18) is detected by a pressure sensor (22), wherein the quantity control valve (30) has an electromagnetic operating device (34) and the quantity control valve (30), with energizing actuation with a first actuation value (66) for the holding current, assumes a closed state (62) and actuation with a second actuation value (64) enables the quantity control valve (30) to assume an open state (60), wherein a borderline holding current of the quantity control valve (30), at which the quantity control valve (30) remains in its closed state, is determined by an adaptation method, characterized in that this borderline holding current is determined in that, in a step (310), an actuation value for the holding current, at which the quantity control valve (30) opens, is set when the pressure has dropped, and the energization of the quantity control valve (30) is extended beyond the bottom dead centre of the high-pressure pump, there being no increase in pressure in the fuel rail (18), and the holding current is gradually incremented from delivery to delivery, and the energization is extended beyond the bottom dead centre of the high-pressure pump with each delivery, wherein, when the quantity control valve (30) remains closed during a delivery stroke which starts after the bottom dead centre of the high-pressure pump and there is an increase in pressure, a current value before the last increment is used as the borderline holding current, the borderline holding current being determined on the basis of the actuation signal with which the increase in pressure takes place.
2. Method according to Claim 1, characterized in that the actuation value which is applied to the quantity control valve (30) after the top dead centre is specified on the basis of the borderline holding current.
3. Method according to either of Claims 1 and 2, characterized in that the adaptation is carried out during idling of the internal combustion engine.
4. Open-loop and/or closed-loop control device (54) for a fuel injection system (10), characterized in that it comprises means for carrying out a method according to any of Claims 1 to 3.
5. Computer program, characterized in that it is programmed to carry out a method according to any of Claims 1 to 3 when it is programmed on an open-loop and/or closed-loop control device (54) according to Claim 4.
6. 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 according to Claim 5 is stored on it.

Images