CN108626048B

CN108626048B - Method for operating a high-pressure pump

Info

Publication number: CN108626048B
Application number: CN201810219017.4A
Authority: CN
Inventors: D.舒勒
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2017-03-17
Filing date: 2018-03-16
Publication date: 2022-04-22
Anticipated expiration: 2038-03-16
Also published as: CN108626048A; DE102017204482A1

Abstract

The invention relates to a method for operating a high-pressure pump of an internal combustion engine, having at least one delivery means to which an electric intake valve is assigned, wherein at least two delivery strokes are used for delivering a predetermined quantity of fuel into the high-pressure reservoir, each delivery stroke being carried out by means of one of the delivery mechanisms, wherein the electromagnet of the respective delivery mechanism is energized with a current characteristic curve comprising at least a boost current for at least one of the at least two delivery strokes, and wherein the electromagnet of the respective delivery means is energized with a current characteristic curve which comprises only a holding current for at least one further delivery stroke of the at least two delivery strokes, the holding current being applied from the preceding delivery stroke of the respective delivery means.

Description

Method for operating a high-pressure pump

Technical Field

The invention relates to a method for operating a high-pressure pump, to a computing unit and to a computer program for carrying out the method.

Background

In combination with a piston pump, an intake valve with a freely movable valve piston can be used as a high-pressure pump for compressing the fuel up to a desired pressure value, a so-called rail pressure, and conducting it into a high-pressure reservoir (so-called common rail). The intake valve is open during an intake stroke of the piston and allows a fuel replenishment flow, and can be actuated during a compression stroke of the piston in such a way that it is closed in order not to allow a fuel flow into the low-pressure region.

For internal combustion engines with high fuel requirements, for example, high-pressure pumps with two (or more) delivery devices can also be used, for which two (or more) delivery devices are separately driven or actuated in order to increase the delivery output of the high-pressure pump.

Disclosure of Invention

According to the invention, a method for operating a high-pressure pump is proposed, as well as a computing unit and a computer program for carrying out the method. Advantageous embodiments are the subject matter of the preferred embodiments and the following description.

The method according to the invention is used for operating a high-pressure pump of an internal combustion engine, which has at least one delivery device, in particular at least one piston delivery device, for delivering fuel, to which an electric intake valve is assigned in each case. In this case, fuel can be supplied to the high-pressure reservoir, in particular from a low-pressure region, via the respective delivery chamber of the respective delivery means. In particular, exactly one or exactly two delivery devices can be provided here, but more delivery devices, for example three or four delivery devices, which are respectively used for delivering fuel, can also be considered.

For each electric suction valve, the armature as a stroke limiting means for the respective valve piston, which separates the low-pressure region from the respective delivery chamber, is preferably adjustable by means of the respective electromagnet between a first position, in which the respective valve piston cannot close, and a second position, in which the respective valve piston can close.

In this case, there is usually no mechanical connection between the stroke limiting mechanism or the armature and the valve piston. A mechanical spring can exert a mechanical spring force on the armature and hold the armature in the initial position. The position of the armature relative to the electromagnet is changed by actuating the respective electric intake valve and thus by energizing the electromagnet, in particular against the spring force of the mechanical spring, so that the stroke limiting mechanism is switched from the first position into the second position. This means that the suction valve is normally open in the currentless state and can only be completely closed in the energized state, if pressure is applied to the valve piston. This can be achieved in this way: although fuel is sucked from the low-pressure region into the respective delivery chamber during the suction phase of the respective delivery mechanism, fuel is then only delivered from the delivery chamber into the high-pressure reservoir during the compression phase if the suction valve is completely closed. Otherwise, fuel is delivered back into the low pressure region during the compression phase.

In order to deliver a predetermined quantity of fuel, at least two delivery strokes are then used, which are each carried out by means of one of the delivery devices. In other words, the predetermined quantity of fuel is distributed over at least two delivery strokes. For at least one of the at least two delivery strokes, the electroinhalation valve and in particular the respective electromagnet of the respective delivery mechanism are then energized with a current characteristic curve which at least comprises a boost current. Such a current characteristic can preferably also have a pick-up current after the boost current and in particular a holding current after the pick-up current. For at least one further delivery stroke of the at least two delivery strokes, the electroinhalation valve is energized with a current characteristic curve which comprises only the holding current and there in particular the respective electromagnet of the respective delivery mechanism. In this case, such a holding current is applied from at least one preceding delivery stroke of the respective delivery means. This means that the corresponding energization must already take place in one of the preceding conveying strokes of the relevant conveying means and must then be maintained. For this preceding delivery stroke, a current characteristic curve can then be used which at least comprises the boost current.

In the proposed method, a predetermined quantity of fuel is thus distributed over at least two delivery strokes in such a way that a full delivery takes place with at least one delivery stroke and a further partial delivery takes place with at least one further delivery stroke (full delivery should also be required if this is not due to the required quantity). This leads to the following results: the quantity of fuel is not distributed uniformly over the delivery stroke, as is usually the case in conventional delivery, but non-uniformly. However, the required amount is delivered overall. It is now particularly advantageous in this connection that no boost current is required during the delivery stroke with full delivery. Although a continuous energization of the electromagnet is required, the overall energy consumption remains approximately the same due to the disappearance of the boost current. However, the particularly troublesome energization promotion and the troublesome generation of the energization current can be eliminated.

The method is particularly preferred in the case of a high-pressure pump having at least two delivery devices. It is then preferred that different delivery mechanisms can be used for the at least two delivery strokes for delivering a predetermined quantity of fuel into the high-pressure reservoir.

Electrical energy, usually from a corresponding controller, is required for each actuation of the electric suction valve. For reasons of noise and also for energy reasons, it may be possible for a high-pressure pump with two or more delivery mechanisms to completely shut off one delivery mechanism and to distribute the quantity of fuel to be delivered to another delivery mechanism or to several other delivery mechanisms in the low load range of the internal combustion engine.

In order to be able to switch also precisely when higher rotational speeds are present or in higher load ranges and for reasons of reproducibility of the quantity of fuel to be delivered, the electric inlet valve is usually energized with a boost current in the initial phase of the energization, i.e. is actuated with a voltage higher than the usual battery voltage, in order to be able to build up a current in the electromagnet more quickly. Such higher voltages have to be generated more or less inconveniently in the controller, which means a not insignificant line overhead. The more energy that generally has to be made available to the electrosuction valve in the operating range by the boost current, the greater the line overhead generally becomes (for example, larger buffer capacitors and larger coils).

The method now uses, in a modified form, the concept of switching off a delivery means in the lower load range or speed range in the case of two or more delivery means, so that the method can also be used in the higher load range or speed range, i.e. in particular also when a predetermined quantity of fuel cannot be achieved with only one delivery stroke.

Due to the continuous energization of at least one of the electric suction valves or the electromagnet thereof, the boost current is no longer necessary, similar to the shut-off. In the case where there are exactly two feeding mechanisms, for example, the number of times of energization with the boost current necessary is halved. As already mentioned, the overall energy requirement remains approximately constant, but the required lines for generating the boost current or the boost voltage can be designed smaller or simpler or, when jointly used, also for other loads (for example fuel injectors).

Although particularly significant advantages result for a high-pressure pump having at least two delivery devices, the concept can also be used advantageously in a high-pressure pump having only one delivery device. In this case, the one delivery means is used for the at least two delivery strokes for delivering a predetermined quantity of fuel into the high-pressure reservoir. The at least one further delivery stroke can expediently follow the at least one delivery stroke, for which a current characteristic curve comprising only the holding current is used, and for which a current characteristic curve comprising at least the boost current is used.

The principle used for the case of two or more conveying means is here applied to one conveying means by: in the same conveying means, corresponding actuation or energization takes place in each case one after the other, with the principle that two or more conveying strokes take place simultaneously, or if the individual conveying means are actuated offset, for example when cams arranged offset from one another on the drive shaft are used, the two or more conveying strokes may take place slightly offset. In this case, for example, every second energization with a boost current can be avoided, which leads to a smaller load on the required lines.

The computing unit according to the invention, for example, a control unit of a motor vehicle, is designed in particular in terms of program technology for carrying out the method according to the invention.

It is also advantageous to implement the method in the form of a computer program, since this results in particularly low costs, in particular if the controller used for execution is also used for further tasks and is therefore already present. Suitable data carriers for providing the computer program are, in particular, magnetic memories, optical memories and electrical memories, such as, for example, a hard disk, flash memories, EEPROMs, DVDs and similar further memories. The program can also be downloaded via a computer network (internet, intranet, etc.).

Further advantages and embodiments of the invention emerge from the description and the drawing.

Drawings

The invention is schematically illustrated in the drawings by means of embodiments and described below with reference to the drawings. Wherein:

fig. 1 shows a schematic representation of a fuel injection system of an internal combustion engine, which has a high-pressure pump with an intake valve, for which the method according to the invention can be carried out;

fig. 2 shows a schematic illustration of a high-pressure pump with a suction valve, for which the method according to the invention can be carried out;

FIG. 3 shows a side view in relation to FIG. 2;

fig. 4a and 4b show schematically in a preferred embodiment the current characteristic curves during the implementation of the method according to the invention; and is

Fig. 5a to 5c show, in various preferred embodiments, the course of the pressure in the high-pressure reservoir during the implementation of the method according to the invention.

Detailed Description

An exemplary fuel injection system 10 for an internal combustion engine 40 is schematically illustrated in FIG. 1. This fuel injection system comprises, in the exemplary embodiment, a (here electric) fuel pump 14, by means of which fuel can be removed from the fuel tank 12 and fed to a high-pressure pump 15 via a fuel filter 13. The area in front of the high-pressure pump 15 thus represents a low-pressure area. The high-pressure pump 15 is usually connected to the internal combustion engine 40 or to its camshaft or crankshaft and can thus be driven.

The high-pressure pump 15 has two electric suction valves 16, 16', which are explained in detail with reference to fig. 2 and 3. The output of the high-pressure pump 15 is connected to a high-pressure accumulator 18, a so-called rail, to which a plurality of fuel injectors 19 are connected. Fuel can again be added to the internal combustion engine 40 via the fuel injector 19. Furthermore, a pressure sensor 20 can be provided on the high-pressure reservoir 18, which is designed to detect the pressure in the high-pressure reservoir 18.

Furthermore, a computer unit 80 embodied as a controller is shown, which is designed in an exemplary manner for actuating the internal combustion engine 40 or the fuel injectors 19 and the high-pressure pump 15 with the electric intake valves 16, 16'. Furthermore, the control unit 80 can, for example, read in the signal of the pressure sensor 20 and in this way can detect and process the pressure in the high-pressure reservoir 18.

The high pressure pump 15 and the electric suction valves 16, 16' of fig. 1 are shown in more detail in fig. 2 and 3. Fig. 3 shows the side view of fig. 2 and more precisely the side view from the left. Fig. 2 and 3 are described more fully below.

The high-pressure pump 15 has a delivery mechanism 23, 23 'which in turn has a piston (pump piston) actuated by a cam 24 or 24', respectively. The cam rests on a shaft 37 and can be arranged on the pump side in a pump housing of the high-pressure pump 15. In particular the cam movement is connected to the internal combustion engine by a suitable connection, for example by a camshaft. The cams 24 and 24' are configured as double cams and are offset by 90 °.

Furthermore, the high-pressure pump 15 has an outlet valve 25, 25 'via which the delivery chamber 26, 26' of the high-pressure pump 15 is connected to the high-pressure reservoir. The outlet valves 25, 25 'can be designed, for example, as check valves by means of springs, so that fuel can be delivered from the respective delivery chamber 26 or 26' into the high-pressure reservoir only when a sufficiently high pressure prevails in the respective delivery chamber.

The electric suction valves 16, 16' each have a valve piston 30 or 30' which separates the low-pressure region from the respective delivery chamber 26 or 26' of the high-pressure pump 15. The fuel flow from the low-pressure region is shown here by means of arrows.

In addition, the electric intake valves 16, 16' each have an electromagnet 32 or 32' with a coil 31 or 31 '. The coil 31, 31' can be connected to the control unit, for example, so that the coil 31, 31' or the electromagnet 32, 32' can be energized over the range of actuation of the electric intake valve. Furthermore, stroke limiting means 33, 33' are provided, which are designed here as armatures for the respective electromagnets.

In the non-energized state of the electromagnet 32 or 32', the armature 33 or 33' can be pressed away from the electromagnet 32 or 32', for example by means of one or more springs, in the direction of the valve piston 30 or 30'. In this currentless state, the respective electric intake valve 16 or 16' is in the first position S, as is shown here by way of example₁In (1).

At the first position S₁The valve piston 30 or 30 'cannot be completely closed or the low-pressure region cannot be completely separated from the delivery chamber 26 or 26', since the armature 33 or 33 'limits the stroke of the valve piston 30 or 30'.

If the coil 31 or 31 'is energized, the armature 33 or 33' moves in the direction of the electromagnet 32 or 32 'and thus away from the valve piston 30 or 30'. In this energized state, the corresponding electric inlet valve is in the second position S by means of the

stroke limiting means

33 or 33₂In (1).

At the second position S₂The valve piston 30 or 30 'can be completely closed or the low-pressure region can be completely separated from the delivery chamber 26 or 26', since the armature 33 or 33 'no longer limits the stroke of the valve piston 30 or 30'. In the closed state, the valve piston 30 or 30' closes the valve seat 35.

The operating principle of the high-pressure pump 15 together with the electric intake valve 16 will now be explained briefly below. In the starting state, the intake valve 16 and in particular the valve piston 30 are open in the currentless state and the outlet valve 25 is closed.

During the intake stroke or intake phase of the part of the high-pressure pump having the piston 23, as this is depicted by the arrow, the cam 24 moves during the rotary movement and the piston 23 moves downward in the direction of the cam 24. Due to the opened suction valve 16, fuel is sucked into the delivery chamber 26.

During the delivery stroke or compression phase of the high-pressure pump 15, the electromagnet 32 is not yet energized first, i.e. the armature 33 is in the first position S₁In (1). The piston 23 moves upward and thereby conveys the fuel from the conveying chamber 26 back in the direction of the fuel pump 14 due to the opened suction valve 16. For this purpose, it is to be noted that the valve piston 30 is not completely closed despite the pressure generated in the delivery chamber 26 or the fuel flow in the direction of the low-pressure region, since the armature 33 limits the stroke of the valve piston 30.

If the coil 31 is now energized, for example also during the compression phase, the armature 33 moves into the second position S₂In (1). The valve piston 30 can thus be pressed into the valve seat 35 by the pressure of the fuel in the delivery chamber 26 or by the fuel flow in the direction of the low-pressure region. The suction valve 16 is thus closed. By a further lifting movement of the piston 23, a further pressure is now built up in the delivery chamber 26. With a sufficiently high pressure, the outlet valve 25 is opened and fuel is delivered into the high-pressure reservoir.

The principle of action of the electric suction valve 16 'corresponds to that of the electric suction valve 16, but the cam 24' is offset by 90 ° in relation to the cam 24, so that a phase shift occurs. This phase shift is produced by the cam 24' with respect to the stroke of the piston 23', but the electric intake valve 16' can also be controlled correspondingly with a phase shift.

Fig. 4a and 4b schematically show, in a preferred embodiment, the current characteristic curves during the implementation of the method according to the invention. For this purpose, the current I is accordingly plotted against the time t.

Fig. 4a shows a current characteristic curve P₁For this current characteristic curve, in order to actuate the electric intake valve, a boost current I is first used in the electromagnet during the delivery stroke_BSubsequently reducing the boost current to a pick-up current I_AAnd then reduced to the holding current I_H. The boost current I is required here_BFor rapidly lifting the armature, the pick-up current I then being required_AFor lifting the armature as far as possible, i.e. up to a stop. And thereafter said holding current I_HIt is sufficient for maintaining the armature in a lifted state.

The current can be cancelled once it is no longer necessary to keep the armature open. This procedure is repeated for the subsequent delivery stroke and thus for the actuation of the electric suction valve. This current characteristic represents, on the one hand, a conventional current characteristic for conventional actuation, but, on the other hand, also a current characteristic as can be used within the scope of the invention for corresponding electrosuction valves which are conventionally actuated with a boost current.

Fig. 4b now shows a current characteristic curve P₂For this current characteristic curve, as in current characteristic curve P₁In that way, the boost current I is initially used for the delivery stroke_BSubsequently reducing the boost current to a pick-up current I_AAnd then reduced to the holding current I_H. But then the holding current I_HOne or more subsequent delivery strokes are maintained. This leads to the following results: the full conveying takes place in these subsequent conveying strokes.

Fig. 5a to 5c show different preferred embodiments of the course of the pressure in the high-pressure reservoir when carrying out the method according to the invention. For this purpose, the pressure p in the high-pressure reservoir is accordingly plotted with respect to time t.

One embodiment is shown in figure 5a,in this embodiment, a high-pressure pump with two delivery devices is used, as described in more detail with reference to fig. 2 and 3, for example. In this case, the delivery stroke Δ t of one of the delivery devices is now set_VIn full transport and over a transport stroke Δ t of the other transport mechanism_TIn the middle of the partial transfer. For this purpose, a manipulation can be carried out as explained in detail with reference to fig. 4a and 4 b. The time offset between the first delivery stroke and the second delivery stroke results here from the offset of the cams, as shown in fig. 2 and 3.

The pressure of the high-pressure accumulator is therefore increased firstly by a greater quantity of fuel and thereafter only by a smaller quantity of fuel. However, they are added together to deliver a predetermined amount. And then at time t_EThe injection takes place by means of a fuel injector, that is to say the pressure is reduced again.

Fig. 5b shows a further embodiment in which a high-pressure pump with two delivery devices is used. The procedure is here similar to the embodiment according to fig. 5a, but here the partial transport is carried out with a first transport stroke and the full transport is carried out with a later transport stroke.

Fig. 5c shows a further embodiment in which a high-pressure pump with only one delivery device is used. Such a high-pressure pump can, for example, likewise correspond to the high-pressure pump described in detail with reference to fig. 2 and 3, but such a high-pressure pump has only one conveying means, i.e. the components shown there in double are only present singly.

Here, with the first delivery stroke, here Δ t_TTo perform a partial delivery, and then to use said second delivery stroke, here at_VTo perform the full conveyance. The time interval between the delivery strokes is greater here, i.e. greater than in the embodiment according to fig. 5a and 5b, since both delivery strokes are carried out by the same delivery mechanism.

It is to be noted here that the portion is implemented in the first delivery strokeSeparately, since the holding current can then be maintained. And then at time t_EThe injection takes place via the fuel injector, that is to say the pressure is reduced again.

It is to be noted that in the case shown here two delivery strokes are required in order to obtain the desired pressure for the injection. If, however, the injection is to take place after a delivery stroke, this method can continue to be used, but then different initial pressure levels are produced for different injections.

Claims

1. Method for operating a high-pressure pump of an internal combustion engine, the high-pressure pump (15) having at least one delivery means (23, 23 ') for delivering fuel, to which an electric intake valve (16, 16') is assigned in each case,

wherein at least two delivery strokes (Delta t) are used for delivering a predetermined amount of fuel_V、Δt_T) The conveying stroke is correspondingly carried out by means of the at least one conveying mechanism (23, 23'),

wherein for at least one of the at least two delivery strokes (Δ t)_T) By including at least a facilitating current (I)_B) Current characteristic curve (P)₁) To energize the electric suction valve (16, 16 ') of said at least one delivery means (23, 23'), and

wherein for at least one other delivery stroke (Δ t) of the at least two delivery strokes_V) By including only the holding current (I)_H) Current characteristic curve (P)₂) To energize the electric intake valve (16, 16 ') of the respective delivery means (23, 23'), the holding current (I) being applied from at least one preceding delivery stroke of the at least one delivery means_H）。

2. The method according to claim 1, wherein for at least one other delivery stroke (Δ t) of said at least two delivery strokes_V) From said respective conveying means (23,23') is loaded with the holding current (I) from at least one preceding delivery stroke_H) In one of the preceding delivery strokes, with at least a boost current (I)_B) To energize the respective electromagnet (32, 32').

3. Method according to claim 1 or 2, wherein, if the high-pressure pump (15) has at least two delivery mechanisms (23, 23'), for the at least two delivery strokes (Δ t) for delivering a predetermined quantity of fuel into the high-pressure reservoir (18)_V、Δt_T) Different transport means (23, 23') are used.

4. Method according to claim 3, wherein for delivering the predetermined quantity of fuel into the high-pressure accumulator (18), at least two delivery strokes (Δ t) are used only when the predetermined quantity cannot be reached with only one delivery stroke_V、Δt_T）。

5. Method according to claim 1 or 2, wherein, if the high-pressure pump has exactly one delivery device, for the at least two delivery strokes (Δ t) for delivering a predetermined quantity of fuel into the high-pressure reservoir_V、Δt_T) The one transport mechanism is used.

6. The method according to claim 5, wherein the at least one further delivery stroke immediately follows the at least one delivery stroke, a current characteristic curve comprising only the holding current being used for the at least one further delivery stroke, and a current characteristic curve comprising at least the boost current being used for the at least one delivery stroke.

7. The method according to claim 1 or 2, wherein said at least one boost current (I) is included_B) At the boost current of (c)I_B) Then additionally has a starting current (I)_A) And at the pick-up current (I)_A) Then has a holding current (I)_H) The pick-up current is used to lift the armature of the electric suction valve up to a stop.

8. A computing unit (80) which is set up for carrying out the method according to one of the preceding claims.

9. A machine-readable storage medium having a computer program stored thereon, which, when executed on a computing unit (80), causes the computing unit (80) to carry out the method according to any one of claims 1 to 7.